Queue large ICS files for background import
Summary: Ref T11801. When a file is larger than 512KB, queue it for background import instead of trying to do it in the foreground, sinc we risk hitting max_execution_time.
Test Plan:
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T11801
Differential Revision: https://secure.phabricator.com/D16805