[req] ILM metrics

[wojtas911]

Hi team, I would like to kindly request ILM metrics in this exporter. What could be exported, is the endpoint that show all ILM status

curl -s "localhost:9200/_all/_ilm/explain"|jq '.indices|map(select(.managed != false))'

then the metrics could be

elasticsearch_ilm_index_status{elasticsearch_ilm_index_status{action="complete",index="test_4",phase="warm",step="complete"} 1

or something similar. I'm open to discussion.

Thank You for considering my request.