fix pathops fuzz bugs

fix pathops fuzz bugs

Fail out in a couple of new places when the input data is very
large and exceeds the limits of the pathops machinery.

Most of the change here plumbs in a way to exclude an assert in
one of these exceptional cases. The current SkAddIntersection
implementation and the inner functions it calls has no way to
report an error to the root caller for an early exit, so rather
than add that in, exclude the assert when the test that would
trigger it runs (allowing the test to otherwise ensure that it
properly fails).

TBR=reed@google.com
BUG=617586,617635
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046713003

Review-Url: https://codereview.chromium.org/2046713003