Beats diagnostic tooling - Phase II

[jlind23]

Following the work done here - elastic/beats#21965

We should now work on collecting metrics and some other tasks:

• Libbeat collects metrics every 10s into ring buffer (N=60)
• Expose internal metrics via API
• elastic-agent diagnostics: filebeat and metricbeat configuration beats#29898
• Diagnostics tool reads metrics ring buffer
• (optional) CLI subcommand diag add to add extra files and directories to a diagnostics report.
  log / capture std from the processes started
• Remove credentials being dumped as part of the diagnotic command

[botelastic]

This issue doesn't have a Team:<team> label.

[ph]

Concerning the credentials, we could add filtering on the exported configuration and replace obvious authorization field, like password, passphrase, token, ssl.key, this would reduce the area of information we could leak. this won't be perfect.

Ideally, the types in the configuration should allow us to do that, but we types aren't known at that time.

[jlind23]

Closing as it is part of other issues :
https://github.com/elastic/ingest-dev/issues/1791