Automate benchmarks to detect regressions

[pjbgf]

Some of flux controllers have operations that are bound by timeouts (GitRepository, Bucket). Automated performance benchmarks would detect deviation in between versions/PRs and allow for quicker response.

From a component level, it would also be valuable to be able to compare and detect deterioration of:

• Resource utilisation.
• Memory leaks.
• Stale connections over time.

https://github.com/fluxcd/source-controller/issues/559