Rewrite OnScreenPositionTest#testImeIsNotBehindNavBar()

This CL rewrites

  OnScreenPositionTest#testImeIsNotBehindNavBar(),

which we added in Android P development cycle [1].

The main motivation of that test was to prevent issues where IMEs were
placed as if there was no nav bar [2], but how the test was
implemented was based on some assumptions about IME-observable insets.

Now that we have a way to test user-perceivable IME visibility [3],
the test is expected to be more robust and compatible if we rewrite it
with InputMethodVisibilityVerifier.

 [1]: I0005aee0259f25c96fb94054535dd945a56e8cfb
      6ff19b02ae5aa75f595a0ebd073b641d6edebf89
 [2]: Bug 11237795, Bug 26984057, Bug 31313118, Bug 33095565,
      Bug 33308065
 [3]: If999aa51fd2e5fd20e9e2d72a7e1dbeb75e3456d
      d7cb355421143641af4cdda38574337cfae3d24c

Bug: 38298890
Fix: 209695046
Test: atest CtsInputMethodTestCases:OnScreenPositionTest
Change-Id: I83e592855c616784be3b62dd9821cf8dd4566916
4 files changed