Introduce FF stop_writing_builds_metadata and update debug_trace_enabled getter/setter

What does this MR do and why?

Context

As part of our CI data reduction project (Reduce growth rate of ci_builds_metadata partit... (&13886)), we introduced a new table ci_job_definitions to help deduplicate job data. Since some data is moved to new destinations (e.g. intrinsic data moved to ci_builds and immutable processing data to ci_job_definitions) we need to be able to use feature flags to read/write data to specific destination.

In #552057 (closed), we ultimately want to move all necessary getter/setters to Ci::Metadatable so they're all in one place and the behaviour can be switched on/off based on feature flags.

This MR

This MR is one of the iterations for the parent issue Move getter/setter methods to `Ci::Metadatable`... (#552057 - closed). Based on the POC: !193948 (closed).

Details:

• Introduces the feature flag stop_writing_builds_metadata (roll-out issue: #552065).
• Adds/updates enabled_debug_trace! in Ci::Metadatable.
  • It writes to the new p_ci_builds.debug_trace_enabled column.
  • It also still writes to metadata if the feature flag is disabled.

References

• Resolves the next step of the implementation plan for Move getter/setter methods to `Ci::Metadatable`... (#552057 - closed)

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Related to #552057 (closed)