For package-managed solutions that set `OSU_EXTERNAL_UPDATE_STREAM`
(which overrides the config value), we should not allow the user to
change the release stream themselves.
Audio offset is integer based in configuration, so let's make sure not
to show that there's an applicable offset when the value difference is
too low.
I've also fixed rounding to match expectations (`AudioOffset` is
precision limited to integer), and handled the case where a user adjusts
the slider but also has a suggested offset – previously it would not
enable the button after slider adjustments but now it will work as
expected.