R1:adf42db5ea2d

Trivially implement RepositoryEditEngine and API methods

Summary: Ref T10748. Ref T10337. This technically implements this stuff, but it does not do anything useful yet. This skips all the hard stuff.

Test Plan:
- Technically used `diffusion.repository.search` to get repository information.
- Technically used `diffusion.repository.edit` to change a repository name.
- Used `editpro/` to edit a repository name.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10337, T10748

Differential…