Spock 2.0 usage in 1.16.0

[musketyr]

If you are Spock user and you are upgrading to 1.16.0 then be sure that you have upgraded to Spock 2.0 before otherwise the Spock tests will no longer be discovered. org.testcontainers:spock:1.16.0 depends on Spock 2.0 which means that it indirectly introduces JUnit 5 so you need to add

test {
    useJUnitPlatform()
}

To re-enable the tests again.

[kiview]

This is the corresponding PR for activating Spock in our own test-suite:
#4568