Refine SwitchImeWindowsFromGestureNavTest

As CL[1] introduced SwitchImeWindowsFromGestureNavTest to verify
IME visibility when switching tasks by gestural navigation.

However, several tests are now has been flaky a while for some reasons:
1) 2 buttons navigation has no longer supported in the new product.
2) 3 buttons navigation is not used for gestural navigation.
3) IME will hide when default setting IME fullscreen mode in landscape
   and focused back to the task that previously IME is shown.
4) Tests might flaky if we are not waiting for splash screen finish.
5) NavBar / Status bar might not visible temporarily during switching
  tasks.
6) IME visiblity will visible / invisiblie when switching between tasks
  with IME visible / invisible.

To fix the above test scenarios, improves the test logic with:
For 1), 2), removed 2 / 3 buttoms navigation from the test parameters.

For 3), since IMF side by default doesn't want to cover the app's
content with fullscreen IME editor disruptively, in case affecting IME
visiblity verfication in landscape, add "flagNoExtractUI" imeOptions
for ImeTestActivity to disable IME fullscreen mode.

For 4), add waitForAppTransitionIdle to ensure the test will going
to next step when finished the splash screen animation.

For 5), 6), uses the tags (start, end, imeVisible / imeInvisible) to
tag the places in the layer traces where we would like to verify the
given layer visiblity (i.e. navBar, statusBar, IME), and make sure we
verified those system window layer visiblity in the right place.

[1]: I677d08543c75746f1405b50eab9061befeb75fc3

Bug: 190139720
Test: atest SwitchImeWindowsFromGestureNavTest
Change-Id: Ifa3b68c710b7fb7f65af5a051a571c76a27371b1