BuiltTargetExtensions and QualitySettings API are excluding/including platforms by string

There might be a missmatch between what the UI inserts, as the UI works NamedBuildTarget and all the API can be called with BuiltTarget.ToString().

Modify the current API to make sure it always works with an string that comes from NamedBuildTarget, otherwise do the translation.

Modify Unit test on Smoke test for BuiltTarget extension.