Simplify selection toolbar state management

Refactors selection toolbar state management
by leveraging binder ordering guarantees for
show/hide/dismiss calls. This change also
removes the onToolbarShowTimeout callback.
Also cleans up widget token and keyed selection
toolbar with a UID on the server side.

Fix: 423124353
Test: manual
Flag: EXEMPT bug fix
Change-Id: Ife9e8cbaca8fec5a17a5637823310a7ca7edd8de