[swarming] Add BQ views task_requests_flat and task_results_flat
[swarming] Add BQ views task_requests_flat and task_results_flat

These BigQuery views enable simpler selection via 'dimensions_flat'.

Bug: 765435
Change-Id: I19024ee47be0e85635cdf03e325aea3164809250
Reviewed-on: https://chromium-review.googlesource.com/c/1483591
Auto-Submit: Marc-Antoine Ruel <d2bf0fc09b08f7b0888b3ddab32b3e89c7122c8b@chromium.org>
Reviewed-by: Quinten Yearsley <747cf52e0cef2e3e9371802a2d344b6c87126a4b@chromium.org>
Commit-Queue: Quinten Yearsley <747cf52e0cef2e3e9371802a2d344b6c87126a4b@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py