This should be the last step in implementing full git worktree support in the GitStore. We still need to add UI for that allows a user to rename a git worktree and, by extension git branches if we use the git picker to do so.

Also, I added a helper function called disallow_guest_request::<T> to the Collab::rpc that is used to specify a proto request isn't allowed to be sent by a guest. This enabled me to add a regression test that checks that a guest isn't allowed to delete a git worktree, without the test hanging forever because it's waiting for the proto server to respond.

Since SSH connections send the proto message directly from client to remote host, this won't affect those requests.

Before you mark this PR as ready for review, make sure that you have:

• Added solid test coverage and/or screenshots from doing manual testing
• Done a self-review taking into account security and performance aspects
• Aligned any UI changes with the UI checklist

Release Notes:

• git: Add SSH support for removing git worktrees