Swap Repository Edit UI to new code

Summary:
Ref T10748. This needs more extensive testing and is sure to have some rough edges, but seems to basically work so far.

Throwing this up so I can work through it more deliberately and make notes.

Test Plan:

• Ran migration.
• Used bin/repository list to list existing repositories.
• Used bin/repository update <repository> to update various repositories.
• Updated a migrated, hosted Git repository.
• Updated a migrated, observed Git repository.
• Converted an observed repository into a hosted repository by toggling the I/O mode of the URI.
• Conveted a hosted repository into an observed repository by toggling it back.
• Created and activated a new empty hosted Git repository.
• Created and activated an observed Git repository.
• Updated a mirrored repository.
• Cloned and pushed over HTTP.
• Tried to HTTP push a read-only repository.
• Cloned and pushed over SSH.
• Tried to SSH push a read-only repository.
• Updated several Mercurial repositories.
• Updated several Subversion repositories.
• Created and edited repositories via the API.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10748

Differential Revision: https://secure.phabricator.com/D15842