feat: add anti-affinity to stateful set

[Panaetius]

closes #820

/deploy #persist

[olevski]

@Panaetius I checked and when the keys are duplicated then the one key later in the file is the one used. So the way that you have set things up things should work.

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-nb-915.dev.renku.ch

[olevski]

I can confirm in the CI deployment that this is working as expected:

renku-ci-nb-915-notebooks-0                            1/1     Running     0          2m35s   10.42.13.25    worker-dev.renku-fat-nodes-2   <none>           <none>
renku-ci-nb-915-notebooks-1                            1/1     Running     0          98s     10.42.3.27     worker-dev.renku-default-6     <none>           <none>

[olevski]

I cannot replicate the previous failure of the integration tests. I think it was caused by some changes happening in the infra at the time where most of the nodes were scaled down a lot and it was hard to schedule things. Rerunning the tests cleared this.

In addition the acceptance tests fail on starting an anonymous session. I tested this in the CI deployment and things work as expected - so it is just a fluke. I can launch an anonymous sessions without a problem.