Add authn-k8s demo app E2E test based on KinD GitHub actions

[diverdane]

Is your feature request related to a problem? Please describe.

The current GitHub actions tests that are performed only go so far as to set up a Conjur
server and then test that it is responsive. It would be good to test deeper, that is, add
tests that set up applications that use authn-k8s (e.g similar to what's done in
examples/kubernetes-in-docker).

If KinD GitHub actions is used for this, one additional benefit would be that we would
be able to test Conjur OSS functionality against the latest releases of Kubernetes
(as well as a handful of older releases to ensure backwards compatibility).

Describe the solution you would like

KinD GitHub actions test is created that does the workflow implemented in
examples/kubernetes-in-docker.

Describe alternatives you have considered

An E2E tests as described could also be implemented in the conjurdemos/kubernetes-conjur-demo
repository.

Additional context