Replace _xpack/monitoring/* with _monitoring/* ES API calls

[ycombinator]

Starting 7.0, the _xpack/monitoring/* API endpoints in Elasticsearch will be deprecated in favor of monitoring/* API endpoints. We should update any references to the deprecated endpoints in the Beats codebase and replace them with the new ones.

[ycombinator]

Pinging @elastic/stack-monitoring

[jakelandis]

@urso @ycombinator - Can we try to get this is in for 7.0.0 ? While testing, I noticed that this can create quite a bit of noise in the logs for Elasticsearch. The change should be easy and /_xpack/monitoring/_bulk --> /_monitoring/bulk. Here is the PR for Logstash: https://github.com/elastic/logstash/pull/10528/files

[ycombinator]

@jakelandis Yes, I will work on this ASAP.

[ycombinator]

Just as an FYI: looks like this somehow got missed in #9656.