Setup Dart recipes in the new repo

This adds most of the machinery needed to support recipes currently in
Chromium's build.git to Dart's recipes repo and copies of the recipes
themselves.

https://crbug.com/1032231

Change-Id: I51011d1a803ddbbe9333293a6b733ab2ba3eb6ac
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/136523
Reviewed-by: William Hesse <whesse@google.com>
Reviewed-by: Robbie Iannucci <iannucci@google.com>
65 files changed