feat($logProvider): add additional control over what gets logged

[lbm]

A simple addition that lets developers have greater control over what does and doesn't get logged. With this change you can disable log, info, warn and error messages, similar to how debug logs could be disable with $logProvider.debugEnabled in the past.

Closes #10560

[lgalfaso]

Hi, thanks for the PR. Anyhow, this is not the right way to make
logging configurable. LogProvider should expose a mechanism to set the
log level, and to know if a specific level is enabled. Just to copy
and paste the mistake that we have for the debug level is not the
right way.

[lbm]

You mean to remove the existing [type]Enabled methods and instead have a unified 'log level', where the level given dictates what type of messages are logged (verbose, warn, etc.)?

[lgalfaso]

I mean that we should keep the existing method to handle just debug
for compatibility reasons, but deprecate it. Then follow the API of an
existing popular library, eg loglevel.