Update certain instrinsic calls in SkSL SPIR-V gen to not mix vectors and scalars.

Functions like min, max, clamp, and mix cannot intermix vectors and scalars as
operands and return value. This updates SkSL to promote scalars to vectors if
need be before calling these functions.

Bug: skia:7653
Change-Id: I13f98d452978e3f15bafddea638b7bbe313d98ce
Reviewed-on: https://skia-review.googlesource.com/110660
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
2 files changed