[Stack Monitoring] Add notes about running a kibana-less deployment to cloud_setup.md

[matschaffer]

https://github.com/elastic/kibana/blob/main/x-pack/plugins/monitoring/dev_docs/how_to/cloud_setup.md shows some basics about how to run a cloud cluster then mentions that the existing kibana will hit problems once you connect a local kibana.

In (internal) https://github.com/elastic/cloud/issues/99247#issuecomment-1070315728 @tobio worked out that you can remove the cloud kibana by running:

ecctl deployment update <id> -f plan.json --prune-orphans

Where plan.json has the kibana key set to [].

We should add this to our docs, and potentially https://docs.elastic.dev/dev/guides/cloud-first-testing to make it easier for other kibana developers to do the same.

[elasticmachine]

Pinging @elastic/infra-monitoring-ui (Team:Infra Monitoring UI)

[tobio]

It should also be possible to bring up a kibana-less deployment through the Terraform provider with something like:

resource "ec_deployment" "just-es" {
  name = "just-es"

  region                 = "us-east-1"
  version                = data.ec_stack.latest.version
  deployment_template_id = "aws-io-optimized-v2"

  # Use the deployment template defaults
  elasticsearch {}
}