[gold] Add ignore rule migration logic.
[gold] Add ignore rule migration logic.

Bug: skia:10582
Change-Id: I2d084e806ba2d85026e8cb5f1b5df3bca335b26e
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/353438
Reviewed-by: Leandro Lovisolo <f558143c2568be8d55575d13f30a1fc5cb8009d5@google.com>
Commit-Queue: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot