Trim dependencies

[amotl]

Problem

The project, due to depending on cratedb-toolkit[testing], pulls in a rather large number of dependencies. Please improve.

[amotl]

This patch will remove the dependency to cratedb-toolkit[testing], so the sandbox installation becomes lighter again.

• Testing: Use native Testcontainers adapter #502

[amotl]

GH-502 is ready, and will remove the dependency to cratedb-toolkit[testing] again, by using the Testcontainers/Python wrapper for CrateDB.