Extend InputMethodStressTest to add more IME show/hide e2e test cases.

Add more IME show/hide test cases to cover different flag settings(window flags, soft input mode flags), show/hide methods (from auto-show/IMM/WIC/Click), call times and user actions.

Merge the two TestActivitys in AutoShowTest and ImeOpenCloseStressTest into one in ImeStressTestUtil.

Modify test type in TEST_MAPPING to "presubmit-large" to avoid timeout.

See go/imf-test-cases for clearer test descriptions and results.

Bug: 242838873
Bug: 240359838

Test: atest com.android.inputmethod.stresstest.AutoShowTest
atest com.android.inputmethod.stresstest.ImeOpenCloseStressTest

Change-Id: Ibff3a85fa5b66c692a2fe8cd69fb1ca521b1b8d8