Generate_stats should handle new step names and put them on new sheets.
Also update the docs to show the KHR tests.

Bug: angleproject:3486
Change-Id: I4fef774d98b0e622182686506376f788a7568376
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1632529Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>