Geo: Show hashed storage warnings on geo nodes page

What does this MR do?

• Geo status task checks for hashed storage => https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8739
• If Geo is enabled with legacy storage, show a warning somewhere (on admin login, admin dashboard, Geo page) that can be dismissed permanently

Screenshots

When hashed storage is disabled

When hashed storage is enabled but a project exists in legacy storage

When hashed storage is enabled and all projects are in hashed storage, or the warning is permanently dismissed

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/8289

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?