[feature] support template hardware migration API

[Kushmaro]

Allow users to migrate hardware templates by invoking the hardware template migration API.

a user, should be able to modify the deployment_template_id field, and migrate their deployment to a different hw template.

data "ec_stack" "latest" {
  version_regex = "7.*"
  region        = "eu-west-1"
}

resource "ec_deployment" "staging" {
  name                   = "omer-test"
  region                 = "eu-west-1"
  version                = data.ec_stack.latest.version
  deployment_template_id = "aws-storage-optimized"   # -> changing to "aws-compute-optimized" for example.

  elasticsearch {

    topology {
        id   = "hot_content"
        size = "1g"
        zone_count = 3
    }

    topology {
        id   = "warm"
        size = "2g"
        zone_count = 2
    }
 }

  kibana {
    topology {
      size = "1g"
      zone_count = 1
  }

  }
}

[linyaru]

https://github.com/elastic/sdh-control-plane/issues/1023#issuecomment-1201872409 indicates that this enhancement might have dependencies on the framework migration. @Kushmaro we'll want to confirm whether this is the case before committing to 0.5.0