Extend AutoShowTest to test more softInputMode flags

Extend AutoShowTest to test the behavior of combining various
softInputMode flags:
  * SOFT_INPUT_STATE_UNSPECIFIED
  * SOFT_INPUT_STATE_HIDDEN
  * SOFT_INPUT_STATE_ALWAYS_HIDDEN
  * SOFT_INPUT_STATE_VISIBLE
  * SOFT_INPUT_STATE_ALWAYS_VISIBLE

softInput adjustment flags:
  * SOFT_INPUT_ADJUST_UNSPECIFIED
  * SOFT_INPUT_ADJUST_RESIZE
  * SOFT_INPUT_ADJUST_PAN
  * SOFT_INPUT_ADJUST_NOTHING

set or not set:
  * SOFT_INPUT_IS_FORWARD_NAVIGATION

Flag SOFT_INPUT_STATE_UNCHANGED was not included for now as it requires
more than one activities.

Bug: 242838873
Bug: 77152727
Test: atest InputMethodStressTest
Change-Id: I21ef8073d0b6a582c108141000e23847be6daf33