When we e.g. generate switch configs (i.e. the ones from pressing the
Super+P or the switch-config key on laptops), try a bit harder to find a
"good" monitor scale.
With "good", it means pick a scale that was used in a previous
configuration. In practice, this means that if you for example have
configured your external monitor to use a specific scale, then pressed
e.g. "built in only", and then switched back to e.g. "external only" or
"linear", the generated configuration will use the scale that was
previously configured.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2479>
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