GM to test (almost) all SkSL Angle/Trigonometric intrinsics

This doesn't include the two-argument version of atan, but covers all
other intrinsics from section 8.1 of the GLES Shading Language 1.00
spec.

Several needed additional plumbing for the CPU backend, but all now
appear correct across CPU and GPU.

Bug: skia:10913

Change-Id: I9933ad549b9914d94c9973c702a06bb177be31b1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/334103
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/gn/gm.gni b/gn/gm.gni
index fe52629..39d000b 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -309,6 +309,7 @@
   "$_gm/rrects.cpp",
   "$_gm/runtimecolorfilter.cpp",
   "$_gm/runtimefunctions.cpp",
+  "$_gm/runtimeintrinsics.cpp",
   "$_gm/runtimeshader.cpp",
   "$_gm/sample_matrix_constant.cpp",
   "$_gm/sample_matrix_variable.cpp",