Kick off indexing for File objects on creation

Summary: Ensures that newly-made `File` objects get indexed into the new ngrams index. Fixes T8788.

Test Plan:
  - uploaded a file with daemons stopped; confirmed no new rows in ngrams table
  - started daemons; confirmed indexing of previously-uploaded files happened
  - uploaded a new file with daemons running; confirmed it got added to the index

Not sure how to test the changes to `PhabricatorFileUploadSource->writeChunkedFile()` and `PhabricatorChunkedFileStorageEngine->allocateChunks()`. I spent a few minutes trying to find their callers, but the first looks like it requires a Diffusion repo and the 2nd is only accessible via Conduit. I can test that stuff if necessary, but it's such a small change that I'm not worried about it.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T8788

Differential Revision: https://secure.phabricator.com/D17718

src/applications/files/uploadsource/PhabricatorFileUploadSource.php

@@ -145,7 +145,7 @@ abstract class PhabricatorFileUploadSource
     }
 
     $file = PhabricatorFile::newChunkedFile($engine, $length, $parameters);
-    $file->save();
+    $file->saveAndIndex();
 
     $rope = $this->getRope();