Evaluate the performance impact of index.mapping.total_fields.limit for metricbeat

[AndersonQ]

The current index.mapping.total_fields.limit for metricbeat (and any beat using the libbeat setup command) is 12,500, which was just increased as 10,000 wan't enough anymore. As this setting can impact elasticsearch's performance, it's important to have actual performance measurements if we're to ever increase it again.

The impacts on performance need to be evaluated for:
- ingest
- search
- dashboards query / load time
- other searches
- if indexes with documents that actually use a large amount of the mapped fields VS documents that use only a small % of the mapped fields. (several different integrations VS just a few)

This is actually a elasticsearch performance investigation, not specifically for metricbeat. Any test might use metricbeat or any other tool capable of producing events similar to what metricbeat might produce.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)