bug#46904: Non-unique windows produced by window-state-put

[Juri Linkov]

We have a problem in window-state-put.  For example, in emacs -Q
evaluate this several times:

(progn
  (window-state-put
   (window-state-get
    (frame-root-window (selected-frame))
    'writable)
   (frame-root-window (selected-frame)) 'safe)
  (selected-window))

Every time the selected window remains the same:

  #<window 3 on *scratch*>

But after splitting the window with e.g. 'C-x 2',
evaluating the same every time creates a new window
that it's expected to do even when there is only one window
on the frame.

I don't know how severe are the consequences.  The only side-effect I noticed
that prev-buffers of restored windows are the same on different tabs because
they share the same window.