Add hashed storage checks to `gitlab:app:check`

What does this MR do?

Adds hashed storage checks to gitlab:app:check:

GitLab configured to store new projects in hashed storage? ... yes
All projects are in hashed storage? ... no
  Try fixing it:
  Please migrate all projects to hashed storage
  as legacy storage is not supported in 13.0 anymore.
  For more information see:
  doc/administration/repository_storage_types.md

This will make sure hashed storage is enabled and all projects are migrated to it, otherwise it will show an error and point to documentation.

We already use this in Geo (gitlab:geo:check) and I'm considering keeping it there as well (it's redundant but they are lightweight and can help reduce some support tickets)

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

Closes #213556 (closed)