feat: add priorityClass to stabilize important apps

[agaudreault]

• Add custom priority classes and assign them to cluster applications to prevents pods like argocd-controller, cert-manager, external-dns, etc to be evicted by demo apps or cron workflow.
• The cluster node should be able to scale up to a limit, but this take times and makes the different demo applications unresponsive during that time.
• Update the bootstrap instructions.

k get pc

NAME                      VALUE        GLOBAL-DEFAULT   AGE
cluster-critical          99999999     false            41s
cluster-low               10000000     false            41s
cluster-medium            50000000     false            41s
gmp-critical              1000000000   false            18d
system-cluster-critical   2000000000   false            18d
system-node-critical      2000001000   false            18d
workflow-controller       1000000      false            17d