Stop using pytest-randomly in tests

[fnesveda]

This removes the pytest-randomly Pytest plugin, as it doesn't play nice with pytest-xdist.

pytest-randomly (among other things) sets the random seed in the beginning of the tests to the current datetime. pytest-xdist runs the tests in parallel in multiple runners. When you use these two together, it happens that all of the runners have the same random seed, so if you e.g. generate random resource names, all runners will generate the same ones, leading to conflicts.

The other feature of pytest-randomly, running the tests in random order to ensure that the tests are not passing just because of some side effects caused by running in a specific order, does not work with pytest-xdist at all, so there are zero benefits of using pytest-randomly at all.