Draft: Resolve "Wikis should only use the normal repository Gitaly RPCs"

What does this MR do?

This is a POC testing replacing the calls to Gollum by regular repository Gitaly RPCs.

This approach makes Gollum basically not necessary at all since we've changed the routes and avoiding it.

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

Related to #36865 (closed)