Re-introduce the Redis set cache for branch and tag names - but don't enable it yet

What does this MR do?

In https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30476, we introduced a cache using Redis sets for branch and tag names. In https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/32408 we revert it because cache invalidation is incorrect in mixed-code environments, such as during a zero-downtime deploy.

This MR reverts that last revert, and adds some code that means we will expire the new keys, but never set or consult them. In %12.4, we can start doing so by changing just a couple of lines in app/models/repository.rb, and a mixed code environment of 12.3 and 12.4 nodes will behave appropriately. This represents an abundance of caution, but will prevent us from expiring (and so needing to re-fill) an expensive cache entry more frequently than necessary.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

Part of #64251 (closed)

Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/65133