mini fx rewrite without merge conflicts

[enp2s0]

Recent commits introduced some merge conflicts with #7242; this PR replaces that one. This PR also does not attempt to make the EffectView resizable or modify the wet/dry behavior and instead just focuses on UI improvements:

• Hide the auto quit decay knob if autoquit is disabled in settings.
• Remove the gate knob.
• Shrink the height of effects from 60px to 35px.
• Use the effect label itself as the button to open the controls rather than a separate button.

The new design in action:

And in the classic theme (as an aside, the new mixer strip design doesn't seem to be compatible at all with the classic theme, but the FX rack is good enough):

~This is mostly complete. Currently hunting down a small bug where the controls button stays in the "open" state even when you close the FX window, but this is likely an easy fix.~ Issue is fixed.

Replaces #7242.