Several refactorings, renaming and improvements.

[Gerrit91]

• Do not sudo rm on Github Actions workspace but only set ownership to runner user
• Add build target for vms image
• Reorder and improve Makefile
  • Use common targets for machine management
  • Don't destroy and re-deploy (aka "reconfigure") containerlab on repeated "up" (--> less destructive)
  • Removed metal-core restart because it works without (?)
  • Cleanup divided into control-plane and partition cleanup
• Improved vm management
  • Added serial console with telnet server access
  • Added script to kill vm
  • Reboot / recreate VMs individually
• Don't use containerlabs prefix to shorten names, renaming to leaf01 --> more similar to what we have everywhere else
• Renamed vagrant partition to mini-lab partition (including network renaming)

[Gerrit91]

I am tempted to throw out the "dev" section where we setup a Docker registry on the switches for developing metal-core. I think it's quite hard to maintain because it's used very rarely. Appears to be a bit too much for this project, which should be as small as possible. External development use-cases should go into their respective projects. @GrigoriyMikhalkin What's your opinion?

[GrigoriyMikhalkin]

I am tempted to throw out the "dev" section where we setup a Docker registry on the switches for developing metal-core. I think it's quite hard to maintain because it's used very rarely. Appears to be a bit too much for this project, which should be as small as possible. External development use-cases should go into their respective projects. @GrigoriyMikhalkin What's your opinion?

Yep, i think we can throw at the moment. At least i didn't use it once)