LocalDisplayAdapterTest - fixed issue with real DDC loading for fake display

Depending on device config file name it is possible that real DDC will be loaded and used in test for FakeDisplay. Introduced method to override/set DisplayDeviceConifg (loaded from mock resources) and used it in probelmatic tests
This fixed testDpiValues and testHdrSdrRatio_notifiesOnChange

Bug: b/284119555
Test: atest LocalDisplayAdapterTest on problematic devices
Change-Id: I67051b4c1a4662b216eb702d04a8a280ea200ec5