test: Run K8sHubble on GKE and 4.9 pipelines
test: Run K8sHubble on GKE and 4.9 pipelines

The Hubble tests check packet trace events that change depending on
whether our kube-proxy replacement is used. We thus run those tests both
on GKE (with our kube-proxy replacement) and on 4.9 (without). We
however don't need to run on all our kernel versions.

This commit only moves all the initialization code into the Hubble
Observe Context, merging BeforeAlls, AfterAll, and variables.

Signed-off-by: Paul Chaignon <a027184a55211cd23e3f3094f1fdc728df5e0500@cilium.io>

tgraf/cilium,cilium/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium