Add menu sliders for FluidSynth chorus, reverb, etc settings

[HydroFS02]

Feel like this would be a nice QoL feature for people using soundfonts through GZDoom's FluidSynth implementation. Adding sliders and option entries for FluidSynth's chorus amount, chorus type, reverb amount, damping, room size, sample rate, and etcetera in the menu under "Advanced Sound Options > Midi player options > FluidSynth". For someone as obsessed with soundfonts and MIDI as I am this would help tremendously for tweaking the settings without going into the config file or console constantly.

Maybe, if possible, the same can be done with Timidity's additional options.