Credential UI should not respond to background taps

The click listener already ignores taps when in non-biometric mode.
However, the view is still included in the accessibility hierarchy.
This change does the following when the UI transitions to credential mode:
  1) removes the click listener for "code correctness"
  2) removes the background view from accessibility hierarchy so that it
     cannot be focused/announced when talk back is enabled

Bug: 143564809

Test: atest AuthContainerViewTest
Test: manual test with talkback enabled
Change-Id: I36727599897a7cec1a99558c6fc2b61f311d1998