This revamps the way that output configs are handled when referencing
an output by both identifier and name. If an output is always referred
to by name or by identifier, this should have no noticeable change. As
soon as there is a name output config and an identifier output config
that matches an output, an output config is generated that is named
`<identifier> on <name>` that is generated with the identifier output
config merged on top of the name output config and stored. When a
change to either is stored, the delta is merged on top of that
"id on name" output config, as well. If the "id on name" output config
exists, it has the highest precedence and will be used when applying
a config to the output.
This fixes the following case:
- `swaymsg output <name> bg /path/to/wallpaper1 fill`
- `swaymsg output <identifier> bg /path/to/wallpaper2 fill`
- `swaymsg output <name> dpms on`
Without this, the wallpaper is changed to `/path/to/wallpaper1`. With
this, the wallpaper remains `/path/to/wallpaper2`.
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