Add performance benchmarks

What does this MR do?

This MR adds performance benchmarks to the semgrep scanner service, so that sast-ide-benchmark can summarise them in the report.

Specifically this MR employs pidstat/sysstat gopsutil to produce the IO statistics.

What are the relevant issue numbers?

Add performance benchmarks to scanner service a... (gitlab-org/gitlab#478056 - closed) • Hua Yan • 17.4 • At risk

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests updated/added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer