WIP: new effect rack interface and features

[enp2s0]

This is still a heavy work-in-progress PR.

• Remove the broken gate knob
• EffectView redesign
  • Remove fixed-width pixmaps; support arbitrary widths; use QT layouts rather than fixed positioning
  • Hide the decay knob if plugin auto quit is disabled
  • Shrink vertical height of effects
  • Make EffectView respect theming options/colors
  • Open effect UI by clicking on effect name a la SongEditor

[Rossmaxx]

It would be beneficial if you add screenshots here.

[michaelgregorius]

I was requested as a reviewer but I am wondering if this PR is already ready for review? The title still says "WIP" and not all checkmarks are checked yet.

[Rossmaxx]

Oops mb. Shouldn't have rushed the review call.

[Rossmaxx]

I converted it to draft because it's a WIP. Change it back if it's ready.

[enp2s0]

yes this is a WIP. Still working on it although I expect to have it wrapped up soon

[Rossmaxx]

If you don't mind, can you spin off the gate knob removal into it's own seperate Pull Request? Makes it easier to review

[enp2s0]

Replaced by #7438.