Set a simple Ime for Ime stress tests

To avoid test failures caused by the default Imes on some test devices overriding some system behavoirs, enable a simple Ime(com.android.apps.inputmethod.simpleime) before test and disable it after test by adding a test rule.

Also merge DisableLockRule, PressHomeBeforeTestRule, ScreenOrientationRule into one ImeStressTestRule.

Lower the height of SimpleIme to prevent keyboard from covering the input box.

Bump up the sdk version of InputMethodStressTests to "current" and fix the falilres in NotificationTest caused by the upgrade.

Test: atest com.android.inputmethod.stresstest
Bug: 271370105
Bug: 271059090
Bug: 271059311
Change-Id: I7bc097b458761424a2d7e9bbef48aa1f7406fcd3