Adding latency metrics to the report and fixing actionsPerLoop

[Chengxuan]

• Actions in a loop are not emitted in parallel. Based on description: This can be helpful when you want to scale the number of actions done in parallel without having to scale the number of workers. I believe it's intended that actions should be triggered in parallel.

It's not clear when should one add more workers vs set more actions per loop to scale the number of requests. My thinking is that we could bind workers to a specific signing address in the future, so if one want multiple requests per signing address then they tune actionsPerWorker if they want more signing addresses to send requests, then they add more workers

• Add latency metrics
• Support for generating an HTML report at the test run
• Report latency metrics in the final report

[shorsher]

LGTM 🚀 thanks @Chengxuan