GlobalActions: Disable IME focusability

GlobalActions is a frequent path to take bugreports; this prevents
it from acquiring the IME focus, which destroys the IME state and
makes IME-related bugreports frequently useless.

Fixes: 156071729
Test: atest GlobalActionsImeTest
Test: Click any text field, long-press power, verify keyboard is still open (behind the power menu)
Change-Id: I396006f3e240c9e410dfa0dab60508d9e2a5ef5d