bug#59208: 29.0.50; tab-bar-auto-width plus display space cpu spin

[Juri Linkov]

> My tab-bar-tab-name-format-function causes 100% cpu spin as of
> ca3763af5c. Disabling tab-bar-auto-width fixes it.
>
> To repro: emacs -Q -l repro.el
>
> repro.el:
>
> (defun aj/tab-bar-tab-name-format (tab i)
>   (propertize
>    (propertize " " 'display '(space :width (8)))
>    'face (funcall tab-bar-tab-face-function tab)))
>
> (setq tab-bar-tab-name-format-function #'aj/tab-bar-tab-name-format)
>
> (tab-bar-mode)

Thanks for the bug report.  Since with
  (propertize " " 'display '(space :width (8)))
the tab width can't grow more than 8 pixels,
a possible fix would be on every iteration
that adds more spaces to the tab name
to check if the tab width remains the same.