Improve Intent disambig dialog behavior

Keep track of last chosen activity for a particular intent, similar
to how it is tracked for "Always" choices.
Pre-select the last chosen activity if previously the user picked
"Just once".
Downgrade "Always" to "Last chosen" if there's a new kid on the block,
instead of removing it entirely.
Add methods to set and get last chosen entry.

UI - switch from Grid to List.

Bug: 9958096

Change-Id: Ied57147739a3ade1d36c3a7ec1e8ce77e5c5bb16