Distribute tests to multiple runners to speed up CI

[elBoberido]

Brief feature description

With cargo nextes it is possible to distribute the execution of tests to multiple runners. This will speed up the CI.

Detailed information

When the number of tests increase, this will have a significant impact on the CI since most of the tests use the RouDiEnvironment which results in ~300ms minimal execution time. Therefore the tests should be distributed to two runners as a starting point.

A CI profile could be used to also add repetition for failed tests.