[Metricbeat][Elasticsearch] Consider applying index metricset optimizations to the cluster_stats metricset

[ChrsMark]

Describe the enhancement:
Consider applying optimizations we did for the index metricset to the cluster_stats metricset:
#16503

This will help in reducing the memory consumption.

Describe a specific use case for the enhancement or feature:
This will be helpful in cases where target ES cluster is quite big and provides big responses making metricbeat consuming a lot of memory to store them in a map as is.

cc: @ycombinator

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[elasticmachine]

Pinging @elastic/stack-monitoring (Stack monitoring)

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[botelastic]

Hi!
We just realized that we haven't looked into this issue in a while. We're sorry!

We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1.
Thank you for your contribution!