Fix invalid mod combinations potentially being selectable at a game level
Add ModUtils class for validating mod usages
The server will return a valid error message in most cases here. We may eventually want to add some fallback message for cases an error may occur that isn't of [InvariantException](https://github.com/ppy/osu-web/blob/3169b33ccc4c540be5f20136393ad5f00d635ff9/app/Exceptions/InvariantException.php#L9-L10) type, but I'm not 100% sure how to identify these just yet.
Improve auto-scrolling logic for drawable channels
For safety purposes... In implementing the previous tests, I found that using mod.Object.GetType() can lead to bad assertions since the same ModProxy class is used for all mocked classes.
Fix PlaylistLoungeTestScene appearing very narrow
Make playlist settings area taller to better match screen aspect ratio