AccessibilityNodeIdManager should hold onto weak references of Views.

... as opposed to strong references.
In case the calls between register and unregister aren't matched, we don't want to be leaking views.
I haven't seen any real eveidence of there being leaks, just a report. But this is preventative.

Created a "WeakSparseArray", which wraps SparseArray, and passes in a kind of WeakReference that has an id.
The references become unreachable, we use the id to remove the the entry from the SparseArray.

Test: Used the device for a bit with talkback on. CTSAccessibility*
Change-Id: I8d11727428f56fc06007232ae341d1409a11991f
Fix: 134506015