R1:d2374c468fdc

Fix missing `willUpload` hook for drag-and-drop chunked upload

Summary:
Ref T9324. When you upload a normal file, we call `willUpload` and then `didUpload`.

When you upload a chunked file, we never call `willUpload`. This can get things out of sync. Make sure we invoke this event for both chunked and non-chunked uploads.

Test Plan: Got cleaner behavior (redirect after all uploads finish) in new Phacility file upload area.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9324

Differential Revision…