Logging API accepts optional Context with priority over trace_id etc, and LoggingHandler passes current Context

[tammy-baylis-swi]

Description

1. Updates Logging API and SDK to accept an additional, optional otel Context at LogRecord init.
2. Adds order-of-precedence so that, if provided Context includes a valid current span, its span information will be used instead of any trace_id, span_id, trace_flags provided at init.
3. LogRecord's to_json does a serialization of what it can in Context (e.g. string, int) then casts to string for other values (e.g. Span).
4. LoggingHandler's _translate inits LogRecord with current context.

Let me know if too many changes for one PR and I can break it up or remove anything out of scope.

Fixes #4328

Replaces #4584

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Added unit test coverage
• Installed SDK changes into my vendor's distro and logs export ok

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated