Only move repos for legacy project storage

What does this MR do?

fixes: #35456 (closed)

After removing most add namespace calls, we noticed there are still quite a few that are happening. It turns out we are calling namespace service for every user rename, even if all of their projects are on hashed storage.

Here is an example: https://log.gitlab.net/goto/6078622d952009761a1eadcef9e1ec43

This MR changes the legacy namespace so that it only cares about moving the namespace directory for projects with legacy namespace.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

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