chore: still keep ctx in git.Repository struct for cat-file batch command (#38684)

Unfortunately, we can't completely remove the ctx from git.Repository,
because the CatFileBatch still heavily depends on a parent context.

If we remove the Repository ctx, the CatFileBatch will become a mess and
create a lot of unnecessary git processes.

http://localhost:3000/-/admin/monitor/perftrace

* Before: open a repo home, dozens of git processes (duplicate cat-file)
* After: only a few (no duplicate cat-file)

services/actions/reusable_workflow.go

@@ -94,7 +94,7 @@ func loadReusableWorkflowSource(ctx context.Context, run *actions_model.ActionRu
 
 // readWorkflowFromRepo loads a workflow file from `repo` at `refOrSHA` and returns its content plus the resolved commit SHA.
 func readWorkflowFromRepo(ctx context.Context, repo *repo_model.Repository, refOrSHA, path string) ([]byte, string, error) {
-	gitRepo, err := git.OpenRepository(repo)
+	gitRepo, err := git.OpenRepository(ctx, repo)
 	if err != nil {
 		return nil, "", fmt.Errorf("open repo %s: %w", repo.FullName(), err)
 	}