Generalize SparseArrayMap.

SparseArrayMap required Strings as keys, which restricted its uses. Now
it can take any object as a key, which better reflects the underlying
ArrayMap generalization.

Bug: 138469672
Test: atest com.android.server.job.controllers.QuotaControllerTest
Test: atest QuotaTrackerTest
Test: atest SparseArrayMapTest
Change-Id: If6da7dfdf3cdd9be0fe9006484c78c574ef2028b