Added Logging SDK Context Injection and Logger Limit

[MarkSeufert]

Note: This PR is going to be updated once the recordable PR gets merged.

This PR makes the following additions to the logging SDK:

• The SDK’s Logger injects the relevant fields of the LogRecord if the user didn’t specify them. The fields that get injected are timestamp, severity, traceid, spanid, and traceflags.
• Added a logger limit to the SDK LoggerProvider (relevant spec issue), where the GetLogger(name) method returns a noop logger if the limit has been reached.
• Unit tests for the above functionality.

The CI tests will fail until the recent API PR gets merged since it uses its trace_flag -> trace_flags change and Severity:kInvalid = 0 change.

cc - @xukaren @alolita @ThomsonTan @lalitb

[MarkSeufert]

Closing this PR for now so the more pressing logging PRs (recordable, ostream exporter, batch log processor) can be reviewed before reopening this one.