Reversion: Tech debt: Revert to KCQL java tests

[davidsloan]

This is a very quick PR to revert the KCQL tests from the scala tests back to the java tests as originally from
https://github.com/lensesio/kafka-connect-query-language/tree/master/src/test/java/com/datamountaineer/kcql

This removes the need to have any scala code in the java-connectors directory.

Please note:

• These aren't my work and I have done the minimum to update them to junit 5 with a few assertJ assertions sprinkled around. I'm not sure this should be reviewed as "new code" but I will aim to address comments nonetheless.
• I have added IDE-generated equals and hashCode methods to some of the KCQL objects.
• I haven't used Lombok for these as this would involve getting Lombok working on the KCQL module for both scala and java. This must also hook in with the Antlr generation so I have left it out of scope for what is supposed to be a relatively quick reversion.
• I have compared the tests in the scala code and java code and ensured changes since the code was switched to scala has been ported to the scala code.