Code coverage in GitHub Actions (Java)

Add code coverage tool for the GitHub actions for Java using Jacoco.
(Challenging)

The multiple test are run in parallel and each need to produce a report that need to be uploaded.
Once all are uploaded a new task have to spawn that combine the reports.
I do not currently know of any solution to this problem, making the whole issue a exploratory process of trial and error, and perhaps a different code coverage tool needs to be used.