Resolve "Geo: Make hashed storage a hard requirement in 12.0"

What does this MR do?

This MR depends on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29586 being merged first, as we need Hashed Storage to be enabled by default on new installations (in order to also not break too many tests)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• 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

Closes #8690 (closed)