Add scripts/generate_deqp_stats.py, which takes in a bot name and prints
out a struct with the number of tests run/passed/failed/etc for each
test suite that ran on the bot.

Bug: angleproject:3369
Change-Id: Ie8086e1d0fb6b141afa388ad44711a798a3bbcd1
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1570111
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>