Clean up the tests and document test policy

[camilamacedo86]

What do you want to happen?

As discussed and agreed in the KubeBuilder meeting on Sep 08 2022: (Meeting: https://youtu.be/GzVcNr_F1SY we just need to support the latest 3 k8s releases and has no reason for we run the tests against so many versions as we do now see:

In this way, we need to:

• - Create a PR to remove the k8s versions 1.18 to 1.22, See: https://github.com/kubernetes/test-infra/blob/master/config/jobs/kubernetes-sigs/kubebuilder/kubebuilder-presubmits.yaml#L112-L261
• - Add to the Contribution guide in the CI/test section that every time that we add a new k8s version to be tested we should remove the old one since our policy to test the project is run against N -2. It can be noted under this section: https://github.com/kubernetes-sigs/kubebuilder/blob/master/CONTRIBUTING.md#where-the-ci-tests-are-configured
• - Clean up the e2e tests. We should remove all tests that are done only in old versions < 1.23:

Following the details
a) Remove all tests done with v1beta1:

• https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/v3/plugin_cluster_test.go#L83-L111
• https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/v3/plugin_cluster_test.go#L134-L145
• https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/v3/plugin_cluster_test.go#L172

(We also need to remove the option to pass version v1beta1)

b) Remove the conditions that will get obsolete

• https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/v3/plugin_cluster_test.go#L148-L154
• https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/v3/plugin_cluster_test.go#L161-L169

c) All tests now are done with restricted mode true then we can remove the test: https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/v3/plugin_cluster_test.go#L172

d) The same changes need to be applied under tests/e2e/v4/, see: https://github.com/kubernetes-sigs/kubebuilder/tree/master/test/e2e/v4

e) we can also remove the skip conditions from : https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/e2e/deployimage/plugin_cluster_test.go

Extra Labels

/kind cleanup

[Eileen-Yu]

Hi @camilamacedo86 I'm very new to the community and is looking forward to join by contribution.

See you've nicely come up with this good-first-issue, and kindly bring detailed instructions.

So based on that, I tried to open 3 PR. Let me know if I'm missing anything.

[26tanishabanik]

@camilamacedo86 , I would like to work on this issue