Flag to allow writing to xwayland clipboard in the background

[Kommynct]

I don't believe writing to the xwayland clipboard in the background will lead to any security issues, as long as it can't read from the clipboard in the background.

It would also solve this bug: #7752

and i'm sure many other xwayland software does garbage like this, pretty much any VM running in xwayland will malfunction like this if it tries to update the clipboard only on focus lost (which is a reasonable optimization in the x.org land)