Description

Add support to set, modify, and filter by trace and spanId fields in LogEntry:

• Both can be set via logging.googleapis.com/* if ingested as structured log (e.g., from a parse_json processor);
• The fields can be used in modify_fields processors;
• The fields can be referred in exclude_logs processors;

Related issue

b/308132501
#1483
#459

How has this been tested?

1. Modified TestModifyFields to cover modify_fields usage of the new fields;
2. Added TestLogEntrySpecialFields to verify the special fields are handled correctly;
3. Added TestExcludeLogsModifyFieldsOrder to cover exclude_logs usage, and the processors are executed in the correct order.
4. Unit tests updated.

Checklist:

• Unit tests
  • Unit tests do not apply.
  • Unit tests have been added/modified and passed for this PR.
• Integration tests
  • Integration tests do not apply.
  • Integration tests have been added/modified and passed for this PR.
• Documentation
  • This PR introduces no user visible changes.
  • This PR introduces user visible changes and the corresponding documentation change has been made. (doc CL prepared)
• Minor version bump
  • This PR introduces no new features.
  • This PR introduces new features, and there is a separate PR to bump the minor version since the last release already.
  • This PR bumps the version.