Make the engine runnable in a testcontainer

[remcowesterhoud]

Description

As of now the engine needs to be embedded on the client side. This has its advantages, because it is very fast to start and stop the engine. However, using the engine as an embedded engine has the consequence that users can't use any Java version that's older that the Java version of the engine. Since the expectation is that some users will still be using Java 8 this would mean the engine can't upgrade to a version higher than 8. This is not what we want.

If we run the engine in a testcontainer we decouple this dependency, and we can upgrade the engine to whatever Java version we'd like.

We also need to open the debug port in the testcontainer and document how to connect to this debug port.

Related issues
Depends on #6
Depends on #24