Save and restore display mode for CtsVerifier

  Save & restore sCurrentDisplayMode in a Bundle, there are cases when the CtsVerifier app is killed and then restored (see b/255265824).
  TestListActivity.sCurrentDisplayMode is static and will be restored with the default value, which causes the wrong test results to be saved.

Test: 1. Toggle folded button to fold mode(enable).
      2. Open CtsVerifier app > Notification Listener Test
      3. Once the test is finished and marked as PASSED, switch to unfolded mode
      4. The test list item should not be marked as passed/failed

Bug: 289019434
Bug: 255265824
Change-Id: Iee93d2dcc69780f35d93c1e5130fe58c356b0531