Add support for Managed Service for Prometheus

[mbarrien]

Adds support for Managed Service for Prometheus to google_container_cluster. Closes https://github.com/hashicorp/terraform-provider-google/issues/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.

[NeckBeardPrince]

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

[SarahFrench]

The linked issue (https://github.com/hashicorp/terraform-provider-google/issues/11224) has been closed by this PR: https://github.com/GoogleCloudPlatform/magic-modules/pull/6104

Closing this PR as stale/superseded