Make clipboard listen to keyboard visibility changes

Currently, we only move to conform to the keyboard visibility on
start. However, when we e.g. come back from the clipboard editor
activity, there's a race condition where the activity (and therefore
the keyboard) is dismissed at the same time as we're showing the
UI. This causes us to display at the height of the keyboard, but
with no keyboard actually visible.

This change adds a listener for keyboard visibility changes so
that if the state changes while we're up, we move appropriately.

Bug: 231574661
Fix: 231574661
Test: manual
Change-Id: I1cbc3bd7dee1d454018dbf5adee860d5941ef1df