Add tests for IME window visibility when setShowWhenLocked

To verify IME window can visible when actvitiy#setShowWhenLocked or
"android:setShowWhenLocked=true" in AndroidManifest.xml,

Added 2 tests in KeyguardLockedTests as below to make sure it works as expected:
1) testShowWhenLockedAttrImeActivityAndShowSoftInput:
   Launch "android:setShowWhenLocked=true" activity & calling showSoftInput
   to verify IME window is visible.

2) testShowWhenLockedImeActivityAndShowSoftInput:
   Launch activity with Activity#setShowWhenLocked set as true & calling
   showSoftInput to verify IME window is visible.

Bug: 119629545
Test: atest KeyguardLockedTests
Change-Id: I1b589bd884395d40395ea87b4fbc9ca04d9ded85
5 files changed