Implement compile-time optimization for distance().

float distance($genType p0, $genType p1);
half distance($genHType p0, $genHType p1);

Change-Id: I492a90c0fe5c950c878752d45c3b2dc6f2cd866e
Bug: skia:12034
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/412379
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
5 files changed