FR: Add interpolation to pipeline processors in the Elasticsearch ingest node

[sachinfrayne]

Describe the feature: Interpolation in the pipeline processor would be an awesome addition to the Elasticsearch ingest nodes: i.e.

POST _ingest/pipeline/_simulate
{
  "pipeline": {
    "processors": [
      {
        "pipeline": {
          "name": "filebeat-{{agent.version}}"
        }
      }
    ]
  },
  "docs": [
    {
      "_source": {
        "message": "foo",
        "agent.version": "6.6.0"
      }
    }
  ]
}

Thanks,

[elasticmachine]

Pinging @elastic/es-core-features