Persistable accessibility ID from ContextWrappers

Only IDs beyond LAST_APP_ACCESSIBILITY_ID can be reliably used for
autofilling. Other ids might change occasionally.

All Views attached to activities get usable IDs. Hence if a
ContextWrapper wraps an activity forward the goodness.

Also make sure that we don't accidentially autofill an unsafe view.

Test: Before the messaging handed out unusable Ids because it uses a
      Contextwrapper. Now it hands out good ideas (accoring to dumpsys)
      CtsAutoFillServiceTestCases
Bug: 38070352
Change-Id: Ibc72c84d77197019939abd231e8960988af7a592