[Improvement] JUnit5 ignores static classes

### What would you like to be improved?

JUnit5 ignores without any warning static methods. While we currently use JUnit4 it's assumed we update to JUnit5 at some Currently startIntegrationTest() is static in AbstractIT and sub-classes.

### How should we improve?

Change to be non-static.

Start by locating startIntegrationTest() in AbstractIT and its subclasses, then inspect how the JUnit4-to-JUnit5 migration affects those methods. Change the methods to be non-static and verify that JUnit5 no longer ignores them by running the relevant integration tests.

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