Docs: added lightweight text based VM guide, added debian-mate-test.md, this is a document to confirm that the Debian Mate Flavour.

Task: [chrisjindu]Simplify the instructions to use a more lightweight VM (text-based) instead of a GNOME-based VM (to allow one to work more on the host instead of inside the VM

This Merge Request adds documentation for running a minimal, text based VM suitable for openQA development. It includes resource recommendations, headless installation guidance, apt-cacher usage, minimal package installs, an example worker configuration, and validation steps. I updated the work_on_tests.md file to reference the new guide.

Added debian-mate-test.md, this is a document to confirm that the Debian Mate Flavour test was successful.