Export {raw, merged} {json, csv} from results.html

[benshayden]

Currently, there are a few ways to extract machine-readable results from results.html:

• The download CSV button downloads a csv file containing merged results.
  • Users can group by traceStart first in order to effectively get the raw results as csv, but this is not intuitive or discoverable.
• tracing/bin/results2json extracts the raw Histograms as json
  • tracing/bin/merge_histograms merges the raw Histograms
  • tracing/bin/histograms2csv converts json Histograms to csv

Navigating these scripts is more difficult than re-running benchmarks with more output-formats, so users are more likely to rerun benchmarks than use these scripts, which wastes a lot of time.

More export options would also facilitate processing results in colab #3806 .

Results.html should offer 3 more buttons to download raw csv, raw json, and merged json results. These 3 buttons along with the existing download merged csv button can be hidden behind a new general Export button.