Remove write to PushRule#project_id from RepositoryController

What does this MR do?

Details in issue: #258649

PushRule#project_id is no longer used as PushRules belong to groups, projects. Previously a PushRule had a 1:1 relationship with a project and this is no longer the case.

• Begins the process of removing push_rules.project_id from the database
• Stops writing to PushRule#project_id when project PushRule is initially created
• Adds delegation from PushRule to ProjectSetting
• Does not affect end-user experience at all

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry No user facing changes
• [-] 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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