Change github workflow to choose which tests to run

[GuiMacielPereira]

Description of work:

There were several changes in this commit:

• The host for running the job changed from self-hosted to ubuntu-latest. This falls in line with the GitHub recommendation to use the default ubuntu-latest for non-private repos. The host was made self-hosted because before the system tests exceeded GitHub's limit. The running time was decreased in a previous commit so using ubuntu-latest is now a viable option.
• Removed some unnecessary comments.
• Added steps that check whether analysis or calibration files were changed using git diff. The result of the check is stored in environment variables analysis-changed and calibration-changed.
• Calibration and analysis tests check the stored environment variables and run accordingly.

To test:

Look at the workflow actions and check that:

• No tests were run in the first commit (no changes to analysis or calibration files)
• The Analysis unit and system tests were triggered after changing analysis files
• The Calibration unit and system tests were triggered after changing the calibration files

Fixes #90 .

[SilkeSchomann]

The workflow file looks good and the different commits did trigger the correct tests (or none in the first case). 👍🏻