Update flag value checks in IME tests

The flag checks in tests should be done using the
DeviceFlagsValueProvider.

Flag: EXEMPT testfix
Bug: 375145734
Test: atest InputMethodInfoTest
  InputMethodManagerTest
  StylusHandwritingTest
  EditorInfoTest
  InputMethodServiceTest
  DefaultImeVisibilityApplierTest
  InputMethodManagerServiceWindowGainedFocusTest
Change-Id: Ibf4182d9fbe745a11d6e9c69b89a30eba34e62e4