build: link stories to unit test to track changes

[aldbr]

• The CI does not identify issues in the stories because they are not really covered
• Unit tests are not really useful at the moment, because most of the tests are done through cypress, but they are still useful to tests components in isolation (could cover potential cases in extensions)
• There are a lot of duplications between the stories and the tests and this can be cumbersome for the developers (we actually stopped writing unit tests)

In this PR I link stories to unit tests: developers will have to create stories for their components, and instead of testing the components, we will test the stories.

• we minimize duplication between stories and unit tests
• we actually test the stories and prevent breaking them

Update:

• we only keep stories corresponding to public components (the ones that will be reused by the community): apps and a few shared components. We don't want to make everything public, because it would be too complex to manage (we would need/risk to break the API too often)
• tests are grouped according to the remaining stories

[aldbr]

It looks like Gubbins extension Tests is failing because of a memory issue that DIRACGrid/diracx-charts#156 would solve.
One train may hide another though 😅

[ryuwd]

The changes all look very sensible to me