Support more transactions types in RepositoryEditEngine

Summary:
Ref T10748. This supports more transaction types in the modern editor and improves validation so Conduit benefits.

You can technically create repositories via diffusion.repository.edit now, although they aren't very useful.

Test Plan:

• Used diffusion.repository.edit to create and edit repositories.
• Used /editpro/ to edit repositories.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10748

Differential Revision: https://secure.phabricator.com/D15740