Optimize SkChopCubicAt to chop at two points at once

Adds an SkChopCubicAt overload that performs two chops at once in
SIMD. Also updates SkChopCubicAt to accept T values of 0 and 1. This
has been the source of bugs in the past.

Bug: skia:10419
Change-Id: Ic8a482a69192fb1685f3766411cbdceed830f9b7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/327436
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed