Fix code generation for Metal and Vulkan with geometric
intrinsics that have scalar versions in GLSL/SkSL, but no
native support in MSL/SPIR-V.
Change-Id: Id4538a00172e0d233ad9d5ed8d33db6436b83208
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/338276
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
