Add a11y click action for keyguard UDFPS

That will bring up the bouncer if user double taps with the
fingerprint sensor selected.

Test: atest UdfpsKeyguardAccessibilityDelegateTest
Bug: 242236225
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ad988ebe0840ef4248e7dd0a33d2930ca621ffb1)
Merged-In: Iaf6a03ef9831a1131cf1df0a6abf35c6cc9b6afe
Change-Id: Iaf6a03ef9831a1131cf1df0a6abf35c6cc9b6afe