Construct AppsFilter cache on background thread

This change moves the initial bootstrapping of the apps filter cache off
onto a secondary thread to avoid impacting the boottime critical path.

Fixes: 162347084
Bug: 161250592
Test: atest AppsFilterTest AppEnumerationTests
Change-Id: Iafa85e838d7f753eaf74037c85f86ee1feeb17aa
(cherry picked from commit 6ab5b297)
Merged-In: Iafa85e838d7f753eaf74037c85f86ee1feeb17aa
Merged-In: Iac2948fb2ad66e45161627f637f039a5f4faf88c