Implement struct == and != on SPIR-V.

OpenGL ES2 allows structs to be compared: http://screen/6KnX4ZfkdLtqDWv
This already worked in GLSL, Metal and SkVM.

Change-Id: Iaf7029c0c1ea9d447348c8280a2788f0d36befad
Bug: skia:11846
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/393598
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
6 files changed