[receiver/elasticsearchreceiver]: Add more metrics

[davidji99]

Enhancement

Add the following metrics for the elasticsearchreceiver:

• indexing_pressure
  (object) Contains indexing pressure statistics for the node.
• discovery
  (object) Contains node discovery statistics for the node.
• ingest
  (object) Contains ingest statistics for the node.
• script
  (object) Contains script statistics for the node.

[github-actions]

Pinging code owners: @djaglowski @BinaryFissionGames. See Adding Labels via Comments if you do not have permissions to add labels yourself.