Use testcontainers to setup OrientDb docker

[mdedetrich]

Replaces manual starting of orientdb docker containers in github actions/docker-compose with https://github.com/testcontainers/testcontainers-scala.

Similar to the other PR's the only notable thing here is that the generated paradox documentation changes slightly, i.e. instead of having

private static String url = "remote:127.0.0.1:2424/";

In the #init-settings its now removed due to the fact that the url is no longer static but retrieved from the newly created docker container. Instead the example code references ORIENTDB_URL/OrientDbUrl constant which in a self explanatory manner describes the same thing.

References https://github.com/akka/alpakka/issues/2841

[mdedetrich]

Test failed due to unrelated link validation, i.e.

`[https://www.2uo.de/myths-about-urandom/`](https://www.2uo.de/myths-about-urandom/%60) status -1 akka.stream.StreamTcpException: Tcp command [Connect(www.2uo.de:443,None,List(),Some(10 seconds),true)] failed because of java.net.ConnectException: Connection refused
 - docs/alpakka/snapshot/ftp.html