Geo: Proxy SSH git operations for repositories that are not yet replicated

What does this MR do?

⚠ Needs:

• gitlab-shell!369 (merged)
• !28181 (merged)
• !29759 (merged)

This MR allows SSH based git clone/pull operations aimed at a Geo secondary to succeed, even if the repository has not been completely replicated. Reasons for why a repository is not completely replicated could be:

• Selective sync is enabled and the repository in question is not selected for synchronisation
• The repository is actively being replicated but has not finished

remote:
remote: This request to a Geo secondary node will be forwarded to the
remote: Geo primary node:
remote:
remote:   ssh://git@geo-primarylocal/namespace/repo.git
remote:

Closes #202037 (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