Set security relevant settings on default node pool to comply with Sentinel

[MajorBreakfast]

This PR adds some security relevant settings to the default node pool that exists temporarily during cluster creation to satisfy Terraform Enterprise Sentinel policies defined by CSO at my project.

[comment-bot-dev]

Thanks for the PR! 🚀
✅ Lint checks have passed.

[MajorBreakfast]

Can you share what the ci failure is about? Prior to raising the PR I planned the private-beta-cluster variant successfully.

[morgante]

This is the error:

       Error: googleapi: Error 400: Cannot use default machine type (e2-medium) with gVisor; choose a different machine type., badRequest
       
         with module.example.module.gke.google_container_cluster.primary,
         on ../../../modules/beta-public-cluster/cluster.tf line 22, in resource "google_container_cluster" "primary":
         22: resource "google_container_cluster" "primary" {

[MajorBreakfast]

@morgante Thank you for the quick feedback!

I've removed the sandbox from the PR to make the tests pass. Sentinel policy enforcement currently only happens for the integrity monitoring, so it's not necessary at this point.

[morgante]

/gcpbuild

[MajorBreakfast]

Change of strategy: Now setting the machine type and image as well based on the value of node pool 0. This should fix it and make it so that even the gvisor can be activated. It makes also a bit more sense that the temporary default node pool uses a machine type matching what's actually used in a real node pool.

[MajorBreakfast]

Green tests ✌️