Testing: Testcontainers for Python

## About
- Similar to GH-54, we would like to demonstrate CrateDB with [testcontainers-python](https://github.com/testcontainers/testcontainers-python), a »Testcontainers« implementation for Python.
- I've started a corresponding implementation on behalf of the [LorryStream](https://github.com/daq-tools/lorrystream) project the other day, and already reused it at the [CrateDB Retention](https://github.com/crate-workbench/cratedb-retention) project. It needs to be reviewed and submitted to the upstream repository as a contribution before further elaborating on it.