* Migrate to python3; drop python support.
* Update Windows toolchain support.
* Remove some unused methods.
* Python 2.7 is still needed on Windows.
* Update gsutil to a version that supports python3.
Fixes: https://github.com/dart-lang/sdk/issues/28793
TEST=Manually tested common user journeys.
Change-Id: I663a22b237a548bb82dc2e601e399e3bc3649211
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/192182
Reviewed-by: William Hesse <whesse@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
Also, delete some unnecessary files from build/fuchsia, and add an async
dispatcher to os_fuchsia.
Change-Id: I477e58d54330e83b2c7b6463395a1212707f8ab7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154162
Reviewed-by: Siva Annamalai <asiva@google.com>
Reviewed-by: Zach Anderson <zra@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Liam Appelbe <liama@google.com>