[Bouncer] Move bouncer expansion callback out...

of KeyguardBouncer.

Bug: 240299776
Test: Build app and open bouncer.
Change-Id: Icb420b506ea614034237b1c0dd7910f2639aff03
Merged-In: Icb420b506ea614034237b1c0dd7910f2639aff03
2 files changed