propapate pipeline.id to api resources

[jsvd]

currently if the pipeline.id changes, the api calls to /_node/pipeline, /_node/stats and /_node/stats/pipeline raise an exception on logstash and return a 503

This PR fixes that and also includes the pipeline id into the documents

for example:

% curl -s localhost:9600/_node/pipeline | jq
{
  "host": "Joaos-MacBook-Pro-5.local",
  "version": "6.0.0-alpha1",
  "http_address": "127.0.0.1:9600",
  "id": "64783f42-7541-4db8-b663-eb4ffb748075",
  "name": "Joaos-MacBook-Pro-5.local",
  "pipeline": {
    "workers": 4,
    "batch_size": 125,
    "batch_delay": 5,
    "config_reload_automatic": false,
    "config_reload_interval": 3,
    "id": "test"
  }
}

[jsvd]

closing in favor of #6606