Make decorations toggleable on a window basis, rather than tied to a layout

[Vermoot]

I'd like to be able to have decorations show and hide at will, either with a keybind, or using ManageHook.

As far as I understand, decorations right now are really tied to a Layout, being a layout modifier. I'm not sure how this works internally but it would make much more sense to me for decorations to be tied to clients rather than layouts, making it much more flexible what you're able to do with them.