Implement sending update frequency of build traces to runner

What does this MR do?

ref: #33658 (closed)

It adds the feature of setting "being-watched" flag for the job when the trace is being watched.

It also adds sending next trace update interval in seconds for the job to the runner as X-GitLab-Trace-Update-Interval in PATCH /jobs/:id/trace response headers when Feature Flag - runner_job_trace_update_interval_header is enabled.

TODO:

• change MR and commit message related to recent decisions about implementation

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team