Playtime: Make it possible to leverage REAPER's "Do not process muted tracks" option

[helgoboss]

Playtime 2 works by registering a so-called preview register for the column's playback track. And it's probably the existence of this preview register that prevents REAPER from not processing the track at all when it's muted. So in theory, all I would need to do is to remove the preview register when pressing the mute button and add it again when unmuting. However, since this also stops clip processing, the clips wouldn't be advanced anymore. They would be stopped when you unmute. Probably not what one would expect. I could build some logic that picks up the clips at the right hypothetical position again, but that might need some more work.

Maybe better to introduce a separate "Deactivate track" button?

Think this through.