Integrate benchmark reporting into `benchmark` command

[marc-gr]

Currently the benchmark command generates benchmark results that are used at a later stage in integrations CI to generate a report comparing them with previous results. We would like to move the code found at https://github.com/elastic/integrations/tree/main/dev/benchreport into this tool for better re usability.

• Move benchreport command logic to elastic-package Add benchmark results comparison reports #1029
  - [ ] Move benchreport Jenkinsfile code to a common library (logic in Jenkinsfile is too integrations specific to extract atm)
• Change xUnit format to ndjson for ease of usage Add benchmark results comparison reports #1029