Support KeyEvent.KEYCODE_ENTER on the keyguard

Attempt #2

On the keyguard, when there's a keyEvent for KEYCODE_ENTER
on action up (not down):
  - If the notification shade is expanded, the notification
    shade will collapse.
  - If the notification shade is not expanded, the primary
    bouncer will show if it's not already showing.

This also updates the logic for the menu and space keycodes to
show the above logic instead of generically collapsing the
notification shade in both cases (which would show the alternate
bouncer instead of the primary bouncer).

Test: `adb shell input keyevent KEYCODE_SPACE`, `KEYCODE_MENU`
and `KEYCODE_ENTER` will dismiss the lockscreen if there's no security,
else the primary bouncer will show. If the notification shade is
expanded on the lockscreen, these commands will collapse the shade.
Test: atest KeyguardKeyEventInteractorTest
Fixes: 270883077

Change-Id: I9d3444dee0149d579a5d3a6d85eac183eeeeba33