add more testing and various improvements

[2bndy5]

• avoid making relative paths from non-project source's path (in parsing clang-tidy stdout)
• conditionally truncate thread comment length
• use FileObj struct to hold FormatAdvice and TidyAdvice instead of instantiating parallel arrays.
• introduce async runtime using tokio. I'm still not sure if I'm using it correctly though.
• start using cached deps in CI (excluding any release builds)
• allow filtering files per clang tool

[codecov]

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[2bndy5]

I also updated the help output. Notice the options are grouped according to functionality:

cpp-linter help

Usage: cpp-linter [OPTIONS] [COMMAND]

Commands:
  version  Display the cpp-linter version and exit.
  help     Print this message or the help of the given subcommand(s)

Options:
  -v, --verbosity <verbosity>  This controls the action's verbosity in the workflow's logs.
                               Supported options are defined by the `logging-level <logging-levels>`_.
                               This option does not affect the verbosity of resulting
                               thread comments or file annotations.
                                [default: info] [possible values: debug, info]
  -V, --version[=<version>]    The desired version of the clang tools to use. Accepted options are
                               strings which can be 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.

                               - Set this option to a blank string (``''``) to use the
                                 platform's default installed version.
                               - This value can also be a path to where the clang tools are
                                 installed (if using a custom install location). All paths specified
                                 here are converted to absolute.
                                [default: ]
  -h, --help                   Print help (see more with '--help')

clang-tidy options:
  -p, --database <database>        The path that is used to read a compile command database.
                                   For example, it can be a CMake build directory in which a file named
                                   compile_commands.json exists (set ``CMAKE_EXPORT_COMPILE_COMMANDS`` to ``ON``).
                                   When no build path is specified, a search for compile_commands.json will be
                                   attempted through all parent paths of the first input file. See
                                   https://clang.llvm.org/docs/HowToSetupToolingForLLVM.html for an        
                                   example of setting up Clang Tooling on a source tree.
  -c, --tidy-checks <tidy-checks>  A comma-separated list of globs with optional ``-`` prefix.
                                   Globs are processed in order of appearance in the list.
                                   Globs without ``-`` prefix add checks with matching names to the set,   
                                   globs with the ``-`` prefix remove checks with matching names from the set of
                                   enabled checks. This option's value is appended to the value of the 'Checks'
                                   option in a .clang-tidy file (if any).

                                   - It is possible to disable clang-tidy entirely by setting this option to
                                     ``'-*'``.
                                   - It is also possible to rely solely on a .clang-tidy config file by    
                                     specifying this option as a blank string (``''``).

                                   See also clang-tidy docs for more info.
                                    [default: boost-*,bugprone-*,performance-*,readability-*,portability-*,modernize-*,clang-analyzer-*,cppcoreguidelines-*]
  -D, --ignore-tidy <ignore-tidy>  Similar to `--ignore` but applied exclusively to files analyzed by clang-tidy. [default: ]
  -x, --extra-arg <extra-arg>      A string of extra arguments passed to clang-tidy for use as
                                   compiler arguments. This can be specified more than once for each       
                                   additional argument. Recommend using quotes around the value and        
                                   avoid using spaces between name and value (use ``=`` instead):

                                   .. code-block:: shell

                                       cpp-linter --extra-arg="-std=c++17" --extra-arg="-Wall"

clang-format options:
  -s, --style <style>                  The style rules to use.

                                       - Set this to ``file`` to have clang-format use the closest relative
                                         .clang-format file.
                                       - Set this to a blank string (``''``) to disable using clang-format 
                                         entirely.
                                        [default: llvm]
  -M, --ignore-format <ignore-format>  Similar to `--ignore` but applied exclusively to files analyzed by clang-format. [default: ]

source options:
  -e, --extensions <extensions>
          A comma-separated list of file extensions to analyze.
           [default: c,h,C,H,cpp,hpp,cc,hh,c++,h++,cxx,hxx]
  -r, --repo-root <repo-root>
          The relative path to the repository root directory. This path is
          relative to the runner's ``GITHUB_WORKSPACE`` environment variable (or
          the current working directory if not using a CI runner).
           [default: .]
  -i, --ignore <ignore>
          Set this option with path(s) to ignore (or not ignore).

          - In the case of multiple paths, you can use `|` to separate each path.
          - There is no need to use ``./`` for each entry; a blank string (``''``)
            represents the repo-root path.
          - This can also have files, but the file's path (relative to
            the :std:option:`--repo-root`) has to be specified with the filename.
          - Submodules are automatically ignored. Hidden directories (beginning
            with a ``.``) are also ignored automatically.
          - Prefix a path with ``!`` to explicitly not ignore it. This can be
            applied to a submodule's path (if desired) but not hidden directories.
          - Glob patterns are not supported here. All asterisk characters (``*``)
            are literal.
           [default: .github|target]
  -l, --lines-changed-only <lines-changed-only>
          This controls what part of the files are analyzed.
          The following values are accepted:

          - ``false``: All lines in a file are analyzed.
          - ``true``: Only lines in the diff that contain additions are analyzed.
          - ``diff``: All lines in the diff are analyzed (including unchanged
            lines but not subtractions).
           [default: true] [possible values: true, false, diff]
  -f, --files-changed-only <files-changed-only>
          Set this option to false to analyze any source files in the repo.
          This is automatically enabled if
          :std:option:`--lines-changed-only` is enabled.

          .. note::
              The ``GITHUB_TOKEN`` should be supplied when running on a
              private repository with this option enabled, otherwise the runner
              does not not have the privilege to list the changed files for an event.

              See `Authenticating with the GITHUB_TOKEN
              <https://docs.github.com/en/actions/reference/authentication-in-a-workflow>`_
           [default: false] [possible values: true, false]

feedback options:
  -g, --thread-comments <thread-comments>
          Set this option to true to enable the use of thread comments as feedback.
          Set this to ``update`` to update an existing comment if one exists;
          the value 'true' will always delete an old comment and post a new one if necessary.

          .. note::
              To use thread comments, the ``GITHUB_TOKEN`` (provided by
              Github to each repository) must be declared as an environment
              variable.

              See `Authenticating with the GITHUB_TOKEN
              <https://docs.github.com/en/actions/reference/authentication-in-a-workflow>`_

          .. hint::
              If run on a private repository, then this feature is
              disabled because the GitHub REST API behaves
              differently for thread comments on a private repository.
           [default: false] [possible values: true, false, updated]
  -t, --no-lgtm <no-lgtm>
          Set this option to true or false to enable or disable the use of a
          thread comment that basically says 'Looks Good To Me' (when all checks pass).

          .. seealso::
              The :std:option:`--thread-comments` option also notes further implications.
           [default: true] [possible values: true, false]
  -w, --step-summary <step-summary>
          Set this option to true or false to enable or disable the use of
          a workflow step summary when the run has concluded.
           [default: false] [possible values: true, false]
  -a, --file-annotations <file-annotations>
          Set this option to false to disable the use of
          file annotations as feedback.
           [default: true] [possible values: true, false]

This also means the generated CLI doc is grouped similarly