Static Analyses for test.only

[daniellanner]

Add a Github job to analyse the test suite and fail upon an occurence of test.only.

When running tests on the local machine it is productive to only run the tests for the feature you are working to minimize wait time. Unfortunately, these changes have been committed made it passed Pull Requests a couple times.

The solution is to add a job to the CI pipeline that checks for test.only occurence before running the unit tests.