Add support for Managed Service for Prometheus

[mbarrien]

Adds support for Managed Service for Prometheus to google_container_cluster. Closes hashicorp/terraform-provider-google#11224

Configuration looks like the following:

resource "google_container_cluster" {
  monitoring_config {
    managed_prometheus {
      enabled = true
    }
  }
}

Open Issues:

• To do this, makes monitoring_config.enabled_components into an optional, to allow configuring just the managed Prometheus component. Without further tests (that might require me to spin up an actual cluster), it's unclear if leaving that empty when enabling just the Prometheus component does the right thing.
• Unclear whether I need to add a ForceSendFields = ["Enabled"] to ensure that prometheus is properly disabled if the component is removed.

[rileykarson]

Do you mind making this against https://github.com/GoogleCloudPlatform/magic-modules? Thanks!

Sorry, there's some docs that need to be updated to point there exclusively, rather than as an option- at one point the environments were pretty much equivalent, but on-PR CI is substantially better there nowadays.

Any files you edited will have a counterpart in https://github.com/GoogleCloudPlatform/magic-modules/tree/main/mmv1/third_party/terraform, so it's just a matter of replaying the changes.

[NeckBeardPrince]

Hasn't this been completed a long time ago? We can close it.