[#143] Set the tag of the docker images to use

[DavideD]

Otherwise we rely on whatever version TestContainer uses as default
and it's not always the latest or could change between updates.

I decided to use the family version where available but we might
want to change this in the future and use the exact version to be
extra safe.

[aguibert]

Historically Testcontainers never changes the default label for exactly this reason -- updating could break users. But I still think it's a good idea to explicitly specify the version so that our docker (testcontainers) and podman devs are always using the same DBs

[DavideD]

I really don't understand the way they choose defaults in TestContainers. If they never update the tag why not always use the latest and clarify it in the javadoc?

Anyway, @aguibert did you also build the PR? GitHub seems to have some problem and cannot test it with the actions

[gavinking]

GitHub seems to have some problem and cannot test it with the actions

The CI is busted since the change to the DB2 database name.

[DavideD]

Thanks, I will check

[DavideD]

Something was wrong with GitHub. It's working now.

[DavideD]

Merged #146