Since the DropDownMenu in the framework has changed it was necessary
to update the GetDropDownItems override of OsuDropDownMenu to
accomodate the new structure of the framework.
When logging in or out the size of the login button would not correctly update,
resulting in a messed-up flow of toolbar buttons. This branch fixes the problem
by avoiding an invalidation-chain-breaking override of Size. Instead, the loginOverlay
bypasses auto sizing by using a new framework feature.