Move persistent_ref.create into run_after_commit

What does this MR do?

Move persistent_ref.create into run_after_commit

Previously, persistent ref creation would hold transaction causing significant delays and increase in 409 errors, and in general slowness when picking CI jobs.

This moves that into run_after_commit hook that still allows us to execute it, but releasing DB lock.

Fixes regression introduced by !17043 (merged)

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

/copy_metadata #36154 (closed)

Resolves #36154 (closed)