Add mute and solo buttons to instrument windows

[rubiefawn]

Resolves #2685 by adding mute and solo controls to instrument windows next to the volume knob.

As of 2025-02-13, this is what it looks like:

[sakertooth]

From the screenshot you provided, it looks like the mute and solo buttons are being merged into the same space as that of the volume knob. I'm thinking having a separate section for the mute and solo buttons (with a label like M/S) might be better.

[rubiefawn]

Here's what that looks like:

[sakertooth]

Here's what that looks like:

That looks a lot better IMO!

[sakertooth]

Code changes look good to me. Will test and wait for CI before approving.

[regulus79]

To me the knobs feel a bit crowded, almost like the pitch range lcd should be moved closer to the channel lcd, idk

[sakertooth]

To me the knobs feel a bit crowded, almost like the pitch range lcd should be moved closer to the channel lcd, idk

I think there was some separation already added before this PR, but since we need that space now it's probably okay to remove.

[rubiefawn]

If we're going to address the lack of real estate in this PR, I would like to move the oversized preset save button to the left of the preset name, and make it the same size as the previous/next instrument buttons.

Wait, do we really need the previous/next instrument buttons in the first place? I don't think I've ever used them, since I just click on the specific instrument I want to edit from the track view.

Here's what it could look like if the previous/next buttons were replaced by the save button (this one is a hasty photoshop job)

[rubiefawn]

After some discussion in the Discord, the save button size and other such layout issues not directly related to the addition of these buttons will be addressed elsewhere.