Make Repository track shard

What does this MR do?

::Repository currently reaches through a container to learn which shard / repository_storage (two names for the same thing; we are moving towards the first) it is on. However, we want to remove container at some point in the future. It looks reasonably plausible from !24376 (diffs)

We instantiate a ::Repository in relatively few places, so this is an easy refactor to make, and it removes the main internal dependency on container / project from ::Repository. External dependencies (e.g. classes calling repository.project) are still numerous, however.

I'm aiming to tackle a few little things a week towards removing them, and this is my first mergable MR in that direction!

Screenshots

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 #201886 (closed)

Related to gitlab-com/www-gitlab-com#6658 (closed)