Update Rspec job factories to write to ci_job_definitions; update tests to stop mutating options & yaml_variables

What does this MR do and why?

Context

We will eventually introduce the feature flag stop_writing_builds_metadata (roll-out issue: #552065 (closed)), which will prevent us from updating metadata attributes such as options and yaml_variables after the job is created. These attributes should not be mutable because we will later populate job_definitions (#551860 (closed)) and that table is insert-only.

We currently mutate these attributes a lot in our spec tests so we need to move away from this approach. Moreover, we need to update the job factories to write to both ci_builds_metadata and ci_job_definitions. If a test mutates options= directly, for example, the change will only update in metadata but not job_definition. As such, the test will break since our code prioritizes reading from job_definition because the FF read_from_new_ci_destinations is default enabled in our specs.

This MR

This MR helps to prepare for the introduction of the FF stop_writing_builds_metadata for options/yaml_variables. Details:

1. Updates the job factory to write to both ci_builds_metadata and ci_job_definitions/ci_job_definition_instances.

• This more accurately represents the data state as we migrate to ci_job_definitions.

2. Updates Ci::Metadatable#degenerate! to also destroy the job_definition_instance record.

• Since this is just a small change, I included it to easily fix the degenerable job tests.

3. Updates the tests to stop mutating options or yaml_variables.

• We only need to address these two attributes for now because they're directly impacted by Ci::Metadatable#read_metadata_attribute which prioritizes reading from job_definition in the tests. The other attributes will be addressed as part of #552057 (closed).

Test updates

I generally implemented one of 3 strategies to fix the tests:

1. Set the value of options/yaml_variables directly in the factory on creation/build.

• This allows us to make changes to the tests in the least invasive way. It also ensures that the options value follows the correct schema (when FF ci_validate_config_options is removed) and that it's being read correctly according to the read_metadata_attribute logic.
• In the future, we could consider refactoring the create tests to use build or build_stubbed (and ensuring .valid?), but for this iteration we're just making the simplest changes.

2. If the object is only created once (e.g. with let_it_be), or the options/yaml_variables value can remain static in the context and option (1) would be impractical, then I stubbed the value with allow(x).to receive(y).and_return(z).

3. For all other cases, the feature flag read_from_new_ci_destinations is stubbed as false.

References

• Resolves Step 2 of the implementation plan for Move getter/setter methods to `Ci::Metadatable`... (#552057 - closed)

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Related to #552057 (closed)