SkSL: Test/implement "geometric" intrinsics

Bug: skia:10913
Change-Id: Ie82354b05db141c8ab90b1a615ddfada4f71a98b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/335049
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
6 files changed