Mongo multi-version testing

[rennokki]

Currently, the docker image used for test is latest, which is 4.2.2. I am pretty sure it's not the only version used by the users and services like AWS DocumentDb are locked to 3.6 for more than a year, for example.

What would be a good solution? LTS branches or matrix to test 3.6, 4.0 and 4.2?

[Smolevich]

I think that we update matrix in ci