Pass screen turning on reason to KeyguardService

Pass a reason int to onScreenTurningOn
callback of KeyguardService, so we can force
SHOW_WALLPAPER flag to true if the display
is switching.

Bug: 395612286
Flag: EXEMPT trivial change
Test: atest PhoneWindowManagerTests
Change-Id: I3e754282076459cbd9792ef06d35b408000f52eb