Frameworks/base: Add removeAll for ArraySet

Add a simple ArraySet.removeAll(ArraySet) method. This avoids two
allocations, a MapCollections helper and an Iterator object, over
the removeAll(Collection) code.

KeySetManagerService heavily calls removeAll during boot (about 9K
times in AOSP). This reduces GC stress and optimizes the removal
(about half the time the removed collection has only one element).
The removal method in KeySetManagerService is also done under a lock,
so that it gates parallelization efforts in PackageManagerService.

Bug: 19498314
Change-Id: Ib0e483adfd09831cd66ab19a820ebf6544a2b66f