Change the back button to close button on more options page

This applies to both the single tap and the autofill-credman
feature. For the latter, we don't propagate the cancellation
exception back to the developer as the user can bring up the
selector again.

Bug: 328086145
Test: Cts

Change-Id: Ib30c49aabe64144c44676ba81535822f9a87889a