Add System Monitor to right click panel when one is found

[corbin-auriti]

This uses category heuristics similar to how we find Terminals for Preferred Applications setting
Also update system settings to use symbolic icon.

Purpose is quick access, feature parity with other desktop environments as a sane default for muscle memory

Forum Discussion and Poll:

https://forums.linuxmint.com/viewtopic.php?t=416628

[corbin-auriti]

Also for reference a similar PR I made was declined before which had hard-coded options which was less ideal #10352

[mtwebster]

Speaking of muscle memory, what about Cinnamon users' muscle memories? :)

Maybe putting it in troubleshooting would be safer? I know I use System Settings here constantly, others probably do as well - this makes it a bit crowded there.

[corbin-auriti]

@mtwebster Done, fair compromise

Pushed changes, and squashed the commits

[haggen88]

This would be a very useful feature for those coming from Windows! It would be more intuitive than modifying the keyboard shortcuts, since in Cinnamon Ctrl+Alt+Delete is not used to launch the system monitor

[mtwebster]

This finds btop for me (which fails to launch because it's a terminal app). You're only using the executable, and ignoring the Terminal=true in the desktop file.

Why not return the appInfo, then appInfo.launch()