Multi-monitor: allow (1) showing panel on all monitors, or (2) cloning a panel to other monitors

[Lurux]

Looking at multi-monitor setups here, there doesn't seem to be an option to show a panel on all monitors, which I assume may due to technical limitations. As such, having an option to duplicate an existing panel to other monitors would be greatly helpful to new users.

See also
https://github.com/orgs/linuxmint/discussions/286
linuxmint/cinnamon#9052

An issue that might pop up if we were to go down the panel duplication route is some of the core applets (wifi, power, sound) seem to be arbitrarily limited to a single instance, I'll draft up a separate proposal about that

See also
https://github.com/orgs/linuxmint/discussions/1428