Provide tooling for analysing xenon / IntervalTimer results

The data from xenon and Interval Timer while useful is hard to consume without building some tooling around interpreting those results.

Ideally there would be a way to transpose the format into another such as the Chrome Tracing format that would allow better performance analysis.

This isn't quite a feature request for hhvm but some tooling related to it.

Format is [defined here](https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/edit?fbclid=IwAR3ffW5ljhq2OcYKeiQqfXY1Nt-xcPSO5XVVZP9vIzc6sWfDAZitEC3fGok)