UV seams per UV channel

It adds more flexibility if we can save UV seams per UV channel.

In a situation when you set up all UV channels but you have feedback with correction on of previous Channels for Albedo texture on the first UV map. But all you seam cuts now for UV lightmap(or different UV map). And you can't just go back. You need to recut needed seams.

Here is a preview of the proposal.

Also, check other proposals on the UV thread

blender.community/c/rightclickselect/x9dbbc/

blender.community/c/rightclickselect/w9dbbc/