workflows: Add e2e tests

Let's make sure we test all the k8s flavours we're interested in, on
every opened PR, and ensure no regressions are added.

CRI-O is being skipped for now as kata-containers' helm chart doesn't
support configuring CRI-O for TEE runtime classes.  Hopefully Red Hat
folks will be able to collaborate with such support at some point.

Signed-off-by: Fabiano Fidêncio <ffidencio@nvidia.com>

Author: fidencio