[Tracing] Add testcase fixed and rejection events to progression task

[ViniciustCosta]

This PR instruments the progression task code in order to emit events for testcases being fixed (TestcaseFixedEvent) or rejected (TestcaseRejectionEvent).

AFAICT there are basically 4 codepaths that change the testcase state to either fixed or invalid (i.e., where the testcase.fixed and testcase.open metadata are updated):

• When it finds the fixed revision range: Emit TestcaseFixedEvent with fixed revision range.
• When it is fixed in the latest custom build (only for custom binary jobs): Emit TestcaseFixedEvent with latest custom build revision.
• When it reaches a bad state of min and max revisions (min >= max): Emit TestcaseRejectionEvent with progression bad state.
• When an expected build no longer exists: Emit TestcaseRejectionEvent with progression build not found.

Testing

• Added unit tests to verify the correct event emit during progression task.
• Testing in runtime will be done by deploying to our development environment.

b/394055138

[ViniciustCosta]

Evidence of this working on development environment: