SkQP: model-creation improvements

  - cut_release/find_commit: use cookies, handle errors.

  - tools/skqp/make_skqp_model.cpp: better error handling

Change-Id: I702e9a13d3a2123c30e3a870fcb942759cfc47c3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257682
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
3 files changed