R1:96ebd358240f

Change repository "Clone/Checkout As" to "Short Name"

Summary:
Ref T4245.

- Rename "Clone/Checkout As" to "Short Name" in the UI.
- Allow any repository to have a short name, not just hosted repositories.

Test Plan:
- Ran migration.
- Reviewed old transactions, saw they looked good.
- Edited an existing repository's short name.
- Gave an imported repository a new short name.
- Removed a repository's short name.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4245

Differential…