feat: add support for _health_report

In elasticsearch 8.7 a new endpoint for cluster health has been added. See https://www.elastic.co/docs/api/doc/elasticsearch/v8/operation/operation-health-report

Author: richardklose

README.md

@@ -62,6 +62,7 @@ elasticsearch_exporter --help
 | collector.snapshots     | 1.0.4rc1              | If true, query stats for the cluster snapshots. (As of v1.7.0, this flag has replaced "es.snapshots").                                                                                                                                                                                                                                                                                | false |
 | es.slm                  |                       | If true, query stats for SLM.                                                                                                                                                                                                                                                                                                                                                         | false |
 | es.data_stream          |                       | If true, query state for Data Steams.                                                                                                                                                                                                                                                                                                                                                 | false |
+| es.health_report        | 1.9.0                 | If true, query the health report (requires elasticsearch 8.7.0 or later)                                                                                                                                                                                                                                                                                                              | false |
 | es.timeout              | 1.0.2                 | Timeout for trying to get stats from Elasticsearch. (ex: 20s)                                                                                                                                                                                                                                                                                                                         | 5s |
 | es.ca                   | 1.0.2                 | Path to PEM file that contains trusted Certificate Authorities for the Elasticsearch connection.                                                                                                                                                                                                                                                                                      | |
 | es.client-private-key   | 1.0.2                 | Path to PEM file that contains the private key for client auth when connecting to Elasticsearch.                                                                                                                                                                                                                                                                                      | |