Respond to tap interrupts when pulsing

Tap interrupts are not sent from SLPI when pulsing because the display
is already on. We need a gesture recognizer and callbacks to do so.

Fixes: 125773800
Test: manually toggle settings and tap on screen
Test: atest ScreenDecorationsTest
Change-Id: I1a5f70ba161209c40d8de9033d09182132f2c8ca