De-flake SimpleIME tests timeouts

This splits the current timeout in SimpleIME tests into one for finding
the button on the screen (using uiDevice), one for waiting for a latch
on an expected event, and one for an unexpected event. Additionally adds
the HW_TIMEOUT_MULTIPLIER to ensure tests run reliably on slower
targets.

Flag: EXEMPT testfix
Bug: 394328311
Test: atest InputMethodServiceTest
Change-Id: I1b7c979a3939dba536bc48b6fef985eb4cda416f