Convert KeyguardTouchHandlingViewModel to Activatable

Following go/sysui-arch:summer-24 to convert the view model into
an Activatable so the lifecycle of coroutines can be automatically
handled in views or composables.

Bug: 406586544
Test: atest SystemUiRoboTests
Test: manual - verify tap to wake with AOD on/off
Test: manual - verify long press launches default settings menu and
touching outside areas will dismiss the settings menu
Test: manual - verify double tap in empty space goes to sleep
Flag: EXEMPT refactor

Change-Id: Ic3314a1e4818379a3f7e306b49855afb35837423