Remove dependency on AsyncTask from MockIme

This is a follow-up CL to our previous CL [1], which enabled MockIme
to be used to test inline-autofill integration with
InputMethodService.

This CL removes the dependency on AsyncTask from MockIme as it is
already deprecated [2].

This CL also removes the use of MockIme#getMainExecutor() as
MockIme.mMainHandle.run() might be a bit more consistent with other
methods in this file.

There should be no change in the actual test expectations.

 [1]: I7b5772550127f840811e7f39db38a404f9d4c29a
      a99b496f2268fe0e1f55220f03524a3f0f343b8f
 [2]: Ie142c281c48bda35f5c8fb01ec8a001e0229fd2e
      0a96c3b965d0180b75bda9c39421b59cc97ebcb4

Fix: 149926050
Test: atest CtsAutoFillServiceTestCases
Test: atest CtsInputMethodTestCases
Change-Id: I0e970b003d799da9e1a866741460390447c2e2f6
1 file changed