Use Testcontainers instead of custom CrateDB integration test helper

[amotl]

Hi there,

the BaseIntegrationTest.java currently uses io.crate.testing.CrateTestCluster and io.crate.testing.CrateTestServer from CrateDB Java Testing Classes. If it is capable enough to replace this layer, we could now use Testcontainers for Java » CrateDB support, thanks to @matriv's contribution testcontainers/testcontainers-java#6790, which has been released yesterday.

With kind regards,
Andreas.

[amotl]

We just added some blueprints how to use Testcontainers for Java with CrateDB.

• Testcontainers for Java: Add showcase examples for different scenarios cratedb-examples#54
• Testcontainers for Java: Add examples for init scripts and function cratedb-examples#59