Currently we override Port._port_specific_expectations_files and define it based on the baseline search path in DarwinPort, WinPort, GtkPort, and WPEPort. This means the only places where we have TestExpectations having a separate search path to baselines are: JscOnlyPort, TestPort, and TestWebKitPort. We shouldn't have totally different behaviour in TestPort and TestWebKitPort to the rest of the world, so we should just define Port._port_specific_expectations_files in terms of Port. baseline_search_path.
Pull request: https://github.com/WebKit/WebKit/pull/26140
<rdar://problem/125435314>