Add stable IDs to multiselect view for talkback

GroupMemberAdapter was not reading _ID column so view ID
was different from Adapter.getItemId. Provide the appropriate
overrides so those IDs stay consistent and talkback doesn't
get confused when views are refreshed.

Bug: 29160869
Bug: 30287073
Change-Id: I87719b0b9f8eede57c036b829dc06f8e52857e97