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)

modules/git/pipeline/lfs_find.go

@@ -32,7 +32,7 @@ func findLFSFileFunc(ctx context.Context, repo *git.Repository, objectID git.Obj
 	results := make([]*LFSResult, 0)
 	// Next feed the commits in order into cat-file --batch, followed by their trees and sub trees as necessary.
 	// so let's create a batch stdin and stdout
-	batch, cancel, err := repo.CatFileBatch(ctx)
+	batch, cancel, err := repo.CatFileBatch()
 	if err != nil {
 		return nil, err
 	}