Debug mode with ssh access to the runner

[MilanKlausz]

Add option to use Debugging with tmate GH action, which allows connecting to github runner through ssh or a web sell:

• [x] Check how tmake action works with multiple env setup matrix elements
• [x] Add a manual_debugging(?) input option to the workflows to enable tmate
• [x] Only use tmate in case of faliure during the fwmk setup or tests. Should be controlled by an input var with this as a default.
• [x] Consider using registered public SSH key(s)
• [ ] Consider input option to handle timeout (first test timed out after 60 min, but could be bacause of being idle for ~30 min?)

[MilanKlausz]

multiple matrix elements work as expected: separate connection strings, separate terminals, and their termination is independent as well.

Note: cancelling the workflow appears not to be working while a tmate session is running. Connecting and then the exit command terminates it.

[MilanKlausz]

This option is now available through the _runtests.yml workflow in the dgcode_actions repo when manually triggering the workflow run (workflow_dispatch event). The 'Launch manual debugging tmate session on failure' input option has to be selected. As the name suggests, the tmate session is only launched in case of a failure. Note that the 'The Package repository' option can be used to select which repository (validations, public/private projects) should be cloned, so the _runtests.yml wokflow facilitates testing all of them, and there are also input fields to handle the branches ('Framework branch to use' and 'Package repository branch')