feat: add enable_k8s_beta_apis support

[maikelpoot]

This PR will expose the enable_k8s_beta_apis:enabled_apis block of the google_container_cluster resource as a list of strings variable.

Example:

module "gke_cluster" {
  source     = "terraform-google-modules/kubernetes-engine/google//modules/beta-private-cluster"
  version    = "38.0.0"
  ...
  enable_k8s_beta_apis = [
    "networking.k8s.io/v1beta1/ipaddresses",
    "networking.k8s.io/v1beta1/servicecidrs"
  ]
  ...
 }

Tested as a local checkout against a cluster that had api's enabled with gcloud cli

[google-cla]

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[apeabody]

Thanks for the contribution @maikelpoot!

[apeabody]

/gcbrun

[apeabody]

/gcbrun

[apeabody]

From the CI Test:

Error: googleapi: Error 400: Beta API "networking.k8s.io/v1beta1/ipaddresses" may only be enabled if Beta API "networking.k8s.io/v1beta1/servicecidrs" is also enabled.

[maikelpoot]

From the CI Test:

Error: googleapi: Error 400: Beta API "networking.k8s.io/v1beta1/ipaddresses" may only be enabled if Beta API "networking.k8s.io/v1beta1/servicecidrs" is also enabled.

Added the requested api to the test fixture

[apeabody]

/gcbrun

[apeabody]

/gcbrun

[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @maikelpoot!