Run more than one assignment in Docker tests

[martinmladenov]

It would be nice to run more than one assignment in Docker CI tests. The Docker tests currently take about 2.5 minutes and this is much shorter than the slowest task, which takes 5.5 minutes. We should run 3 or 4 assignments per category - this won't affect the duration of the overall pipeline as different tasks runs in parallel.

https://github.com/SERG-Delft/andy/pull/236#discussion_r1269839638_

[Arraying]

Don't we already do this? How is it different from what this does?

[martinmladenov]

Yes, we currently run all. But in #236 we are changing it to run only one. We decided it would be nice to run a couple more but made it into another issue.

[alexcojocaru2002]

I can maybe do this @martinmladenov

[mauricioaniche]

Go for it, @alexcojocaru2002