Reland "Use integer patchset and issue variables."

This is a reland of 50b1248ed82a0213ca99f886a31e9ed7c7175b8e

Fixes from the original are in PS2. Change several recipes to use the
shared 'is_trybot' variable, and explicitly check for 0 rather than
relying on patch_ref not being set.

Original change's description:
> Use integer patchset and issue variables.
>
> See https://skia-review.googlesource.com/c/buildbot/+/246397/
>
> Change-Id: I39dae809abdc63007f65bc05040809d1a870b118
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/246302
> Commit-Queue: Ben Wagner aka dogben <benjaminwagner@google.com>
> Reviewed-by: Eric Boren <borenet@google.com>

Change-Id: Ibe1d4f0dc1dc61c39eee6c980bd7509fc260101b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/246919
Commit-Queue: Eric Boren <borenet@google.com>
Auto-Submit: Ben Wagner aka dogben <benjaminwagner@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
26 files changed