delete pod security policy, enable network explorer functional tests

[omrozowicz-splunk]

Description:
Delete deprecated PodSecurityPolicy so Network Explorer can work again.

Issue: #896

Testing: Manual tests + enabling network explorer in functional tests

Documentation: No documentation needed.

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I tested it on microk8s cluster, network explorer pods were initialised successfully and network metrics were gathered:

I don't see all the documented ones, but I don't have any errors so it might be they're not present on my env.

• I wanted to use functional tests we have now to test if behaviour is the same as before deprecation, but looks like network metrics were never tested there (as the condition was events >= 0), I spent some time to try to make network explorer work on minikube to make it a part of testing CI, but that still not sure if it is achievable. Now I see it's going to be disabled completely: End to end tests in Golang #951, so no need for me to work any further on it.

[atoulme]

Indeed. We will bring back network explorer tests in a bit.