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/git_ui/src/commit_modal.rs

@@ -234,7 +234,7 @@ impl CommitModal {
 
         let branch = active_repo
             .as_ref()
-            .and_then(|repo| repo.read(cx).repository_entry.branch())
+            .and_then(|repo| repo.read(cx).branch.as_ref())
             .map(|b| b.name.clone())
             .unwrap_or_else(|| "<no branch>".into());