Cleanup ResolutionPreferenceFragmentTest

- Removed duplicated test (testCreateAndStart and
testCreateAndStartDefaultDisplayNotAllowed). Both tests are basically
the same since both -1 and 0 id not in set up displays
- Make TestableResolutionPreferenceFragment static class, this is to be
used in the next CL so this fragment can be added to a test Activity (to
validate `Activity.finishFragment()`
- Make displayId as initFragment param, as it should be init only once
when fragment started
- Modify to use displays[id] rather than specifying numbers

Bug: 407007697
Test: atest ResolutionPreferenceFragmentTest
Flag: EXEMPT cleanup test
Change-Id: I81f4696f13e4e64acd3e70e09098b130f5d87d43