Revert "fetch and update shortcut icons in background thread"

This reverts commit 4ec390e490dfb1503909853eb55df85f79e9813a.

Reason for revert: the code change introduces significant delay when saving deep shortcut icons in cache.

Bug: 142514365
Change-Id: If7a69844aba7f32690ff347f2db11f0a8041b9e4
5 files changed