give up if huge paths have unresolvable coincidence

This fuzzy test has enormous curves with coincidence runs that break numerics.
If the computed intersections identify that the span of coincidence has been deleted,
give up and return that the path op failed.

TBR=reed@google.com
BUG=597926
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1854333002

Review URL: https://codereview.chromium.org/1854333002
4 files changed