Hot Corner: Add action "Lock & Suspend"

## Prerequisites
- [x] I have searched open and closed issues for duplicates.

## Feature

It would be awesome to have a native option for "Suspend" for a Hot Corner. I quite often use this, because I use my Laptop in office spaces, where I don't want anyone be able to glimpse on my screen while I'm away.

For now I'm using the Custom command `systemctl suspend` as workaround - and to fix going to sleep mode again after unlocking, I'm also moving the cursor position before suspending (installed an extra tool for this): `sh -c "xdotool mousemove 500 500 && systemctl suspend"`

**EDIT:** Updated workaround command to also deactivate the Screen.
**EDIT 2:** Changed "Lock Screen" to "Suspend", because this behaves as intended: It locks the session, deactivates the screen and then goes to sleep mode to save battery.

No source file or test is named. Start by locating the Hot Corner action definitions in settings-desktop and compare the requested action with the existing options; done means the action locks the session, deactivates the screen, and suspends the system without the custom systemctl and xdotool workaround.

Written by the indexing model from the issue text.