Parallelize GH actions build

[blaumeiser-at-bosch]

Summary of the Improvement

We can improve the build time by separating the testing of example projects in the GH actions into several jobs which can be executed in parallel. This should speed up the build time.

Acceptance Criteria

• The separate testing tasks are distributed into jobs and executed in parallel

Definition of Done

• Acceptance criteria fulfilled
• The ticket describes what has been done and describes how the results can be verified (e.g. new Jenkins step is inserted, the report can be viewed at X)
• All known limitations are listed and it is described how they will be addressed (e.g., a ticket for the remaining stuff)
• Documentation is updated
• The result has been reviewed: Everything works as described and can be verified reading only the documentation