Fix Ruby 2.7 keyword args warnings on Repository

What does this MR do?

Fix Ruby 2.7 keywords argument warnings in Repository model.

This change also improves the existing delegation patterns with method_missing implementation.

• The lookup delegation is extracted out of method_missing to a separate method and handle caching for nil value.
• Other method delegation is handled by delegate_missing_to which can handle keyword arguments for both Ruby 2.7 and 3.0.

Contributes to #257438 (closed)

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
• [-] 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