Add fall-back binary search for cubic roots when splitting

This exists in the Pathops version [1] but was not initially
included when switching algorithms from Pathops to base [2].

[1] https://github.com/google/skia/blob/dc6cc023adbfec496e4dfdcbc38022c4079c2d0b/src/pathops/SkDCubicLineIntersection.cpp#L182-L186
[2] https://skia-review.googlesource.com/c/skia/+/633458

Change-Id: I81a870e51512ea38344828ed8dbd1a8ac6b3ee3b
Bug: oss-fuzz:55680
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/641596
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
5 files changed