Reduce calls to git cat-file -s (#14682)

* Reduce calls to git cat-file -s

There are multiple places where there are repeated calls to git cat-file
-s due to the blobs not being created with their size.

Through judicious use of git ls-tree -l and slight adjustments to the
indexer code we can avoid a lot of these calls.

* simplify by always expecting the long format

* Also always set the sized field and tell the indexer the update is sized

modules/git/tree_entry_nogogit.go

@@ -87,5 +87,7 @@ func (te *TreeEntry) Blob() *Blob {
 		ID:       te.ID,
 		repoPath: te.ptree.repo.Path,
 		name:     te.Name(),
+		size:     te.size,
+		gotSize:  te.sized,
 	}
 }