[3.3.x] Equalizer: simplify UI implementation, make sure that the current state is saved and actually being displayed on the next run

The previous logic to store the current state was overly complex to implement a simple lookup and never stored the enabled state to the settings, just the disabled state.

The previous profile selector used 18 buttons, a stack view and a scroll view to reimplement a UITableView that could not show a selected state. This is re-written with a UITableView to actually indicate the currently selected profile and to save 50% of the LoC. Beyond that, the visual appearance is unchanged.

Finally, the equalizer view is reloaded on appearance to reflect the state stored in the user defaults instead of the default values.

This fixes #1289 (closed) while #502 (closed) is left-open for future implementation.

Backport of !714 (merged).