Finish removing git repository state and scanning logic from worktrees (#27568)

This PR completes the process of moving git repository state storage and
scanning logic from the worktree crate to `project::git_store`.

Release Notes:

- N/A

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Conrad <conrad@zed.dev>

crates/project/src/connection_manager.rs

@@ -91,7 +91,7 @@ impl Manager {
                         for (id, repository) in project.repositories(cx) {
                             repositories.push(proto::RejoinRepository {
                                 id: id.to_proto(),
-                                scan_id: repository.read(cx).completed_scan_id as u64,
+                                scan_id: repository.read(cx).scan_id,
                             });
                         }
                         for worktree in project.worktrees(cx) {