Make Gang Jobs Work in The simulator

[d80tb7]

• You can now define a GangCardinality label on a JobTemplate. If this is specified then the jobs will be divided up into gangs wit the given cardinality.
• Nodes get a label of armadaproject.io/clusterName so that the restriction of one gang per cluster works.
• Gang accounting maps are now populated so that gang preemption works as expected.
• There are a couple of unit tests to assert the above.

Outstanding issues are:

• Gang job durations are not correlated. I.e. they will take the shifted exponential of the workflow. I think the simplest thing to do is to have all gang jobs for a given gang finish at the same time. A slightly better approach would be to have all gang jobs finish within a short time.
• Re submission after preemption will not work properly if some jobs in the gang have finished, but others haven't. That's because the resubmission code will only resubmit the preempted jobs. As a result you'll have a partial gang resubmitted which can never be scheduled. Solution here is to make the resubmission code resubmit the whole gang, but I want to fiirst break out that logic into a simple workflow manager struct, such that we can separate out workflow management from the main simulator.