Update testing suite

[akeeste]

This PR:

• adds a setup job to every test that removes the slprj folder so that tests can be rerun most robustly locally when multiple matlab versions are being used
• updates the versions of GitHub Actions to the current releases
• adds calls to close_system and closes each simulink model after running so that there are no naming conflicts as the entire test suite runs

[akeeste]

The calls rmdir to remove the slprj do pose a slight risk to the user locally since directories are being forcibly deleted. This specific function (identical across all tests) identifies and removes only directories named exactly slprj within the current working directory of that test file. This should typically be perfectly safe