[FR] epic: expose offload to general user

[nift4]

• make a whitelist of devices (only gapful works/all works/nothing works) and remove user UI toggle for no-gapless
• fix [BUG] offload is disabled when metadata track is selected, even though metadata track does not hurt #701
• add warning dialog when enabling offload+RG on device where DPE is offloadable, to note that equalizer apps are 99% gonna break RG
• disallow enabling offload+RG on device where it isn't as it won't work