Add more FlickerTests for verifying IME transition

Making sure CL[1] can resolve IME flickers when
- App with IME transiting from a fixed orientation task
- App with IME transiting to the overview screen

[1]: I332c0e4fff62df5d7b793eda2767bb58fe85a938

Fix: 224407658
Test: atest FlickerTests:OpenImeWindowFromFixedOrientationAppTest
Test: atest FlickerTests:OpenImeWindowToOverViewTest
Change-Id: I3120d403b850418a87f57472b91674b0165982b0