port junit4 tests to junit5

[jurgenvinju]

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Because the compiler generates junit5 tests (see usethesource/rascalcore project) we can not run Rascal interpreter-based tests in the same project where the compiler is also used.

A really complex maven pom.xml might be able to run both junit4 and junit5 tests, but it would be better if we can avoid this complexity.

so the proposal is to rewrite the JUnitTestRunners for Rascal (parallel and not parallel) to the JUnit5 framework.

are there any volunteers?