Migrate away from PerformanceTestCaseJunit4

[vogella]

The performance tests in this repo extend PerformanceTestCaseJunit4.

@HeikoKlare did you already define or execute a migration strategy for these tests?

[HeikoKlare]

I don't remember using any specific strategy but I won't expect it to be necessary either. There is PerformanceTestCaseJunit5 as a replacement for PerformanceTestCaseJunit4 which is identical but just uses appropriate means to embed the setUp/tearDown methods for JUnit 5. Apart from that, it should be possible to migrate the test classes themselves in a "default" way (replace annotations, migrate assertions and exchange rules with extensions).

[vogella]

EditorSwitchTest.java opens around 500 terminal windows with vi on my machine, I need to fix that before working on the migration. 500 terminals kill my machine.