fix(graphite): update indexed keys with names

[kevinlacotaco]

Your checklist for a pull request to sitespeed.io

Please review the guidelines for contributing to this repository.

• I'm making a big change or adding functionality so I've already opened an issue proposing the change to other contributors, so I got feedback on the idea before took the time to write precious code
• Check that your change/fix has corresponding unit tests (if applicable)
• Squash commits so it looks sane
• Update the documentation https://github.com/sitespeedio/sitespeed.io/tree/master/docs in another PR
• Verify that the test works by running npm test and test linting by npm run lint

Description

Please describe your pull request and tell us the fix #

Rename user timings and assets when running in perIteration mode. Fixes #2693

It is as late as we can rename the metrics while also knowing that we are running a per-iteration mode. It is right before it is sent out and should have no impact on anything downstream since it just rewrites the key instead of the object used for analysis.

Thank you for making sitespeed.io even better!

[soulgalore]

Hi @kevinlacotaco thank you! I'll release this later this week. Wanna push a new version before the 22nd of October since that day it will be both a new Chrome & Firefox and want to do a release with just updated browsers.