Add SkFUZZF to help whitelist imagefilter fuzz failures

The current use case for this is whitelisting MergeImageFilter failures when the number of inputs is too big. Presumably there will be other whitelisting use cases as we progress.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1873463002

Review URL: https://codereview.chromium.org/1873463002
3 files changed