Refactor repo contents API and add "contents-ext" API (#34822)

See the updated swagger document for details.

modules/lfs/pointer_scanner_gogit.go

@@ -31,7 +31,7 @@ func SearchPointerBlobs(ctx context.Context, repo *git.Repository, pointerChan c
 			default:
 			}
 
-			if blob.Size > blobSizeCutoff {
+			if blob.Size > MetaFileMaxSize {
 				return nil
 			}