Buildbot framework should support a Sidecar

Connectors depend on a MariaDB Server installation to run their test suites.
As new Buildbot architecture demands containerized environments, it is preferable to avoid a server installation on every build.
The lack of systemd in a container environment adds to the motivation to implement a sidecar.

Having a sidecar, i.e. a MariaDB-Server docker container running alongside
the main build (Connectors) can save up time (no installation), offers flexibility (can easily pin the required server version to test with)
and keeps the container environment lightweight and scoped.

The purpose of this task is to implement a mechanism in new-bb that will allow
builds to start a MariaDB Server container in the background, on the host that was chosen as the worker node for the build.