Handle custom key gestures added by the user

DD: go/customizable_shortcuts
PRD: go/custom-kb-shortcuts

Bug: 365064144
Test: atest InputTests:CustomInputGestureManagerTests
Flag: com.android.hardware.input.enable_customizable_input_gestures
Change-Id: I3d3f18558174fb9cc5ec03b3808a357ff0aa2b5b