[Feature]: Handle display option in Wayland

[Caellian]

Conky currently assumes a single output/monitor is available and:

• uses dimension information of last reported/connected monitor,
• requests placement on last focused/used monitor,
• display option is currently ignored in Wayland.

Wayland uses a different naming for displays than X11.

• X11 format is: hostname:number.screen_number, used by display_name in x11-settings.cc
  • basically :0 is a single X11 instance. :0.0 is the first, :0.1 is the second monitor on that instance, etc. Xinerama & RandR abstract this away and create a single "workspace" on :0.0 that spans all :0.N displays.
• Wayland doesn't assign any number IDs to outputs from wl_output events.
  • Users might want to specify displays with description which is a manufacturer name of the display.
    • Only guaranteed to be correct with xdg-output protocol. But likely is with the core protocol as well.

hostname:number.screen_number can be translated to wayland socket and wl_output.

• number is similar to socket wayland-<number>.
• screen_number is the ordinal number of reported wl_output.

On wayland wl_output name is a unique output identifier (per-session).

We'd need to:

• Collect wl_outputs into an array to get a mapping to their indices.
• Handle hotplugging by removing monitors on wl_registry::global_remove and handling additions.
  • Needs some way to re-trigger initialization logic for surfaces.