Docs: Logstash 8.16.0 release docs

[karenzone]

Logstash release manager: @edmocosta Logstash tech writer: @karenzone Docs release manager: @eedugon

Logstash release docs

• [ ] Day after FF, cut branches:
  • [ ] logstash
  • [x] logstash-docs
  • [x] ingest-docs
    • [ ] Update backport tooling for ingest-docs: https://github.com/elastic/ingest-docs/pull/1385
    • [ ] Update backport labels:
• [ ] Release notes:
  • [ ] Add link to docs release issue:
  • [ ] Verify that release notes PR is forwardported to main:
• [ ] Verify that release notes PR is forwardported to 8.x:
• [ ] Update plugin docs:
  • [ ] Bump lock file: https://github.com/elastic/logstash/pull/16561

Special considerations

• [ ] Impact of Health API in 8.16.0 - what to expect on a comparison with previous versions