[ir][msl] Emit some core builtins.

Add support to the MSL printer for the core builtins which can be
emitted directly in MSL.

Bug: tint:1967
Change-Id: I647c4aa7f11af0af207509f6e27bba68acd80a75
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/162505
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: dan sinclair <dsinclair@chromium.org>
diff --git a/test/tint/builtins/gen/var/textureLoad/dd8776.wgsl.expected.ir.msl b/test/tint/builtins/gen/var/textureLoad/dd8776.wgsl.expected.ir.msl
index f6a69b0..c55d7bc 100644
--- a/test/tint/builtins/gen/var/textureLoad/dd8776.wgsl.expected.ir.msl
+++ b/test/tint/builtins/gen/var/textureLoad/dd8776.wgsl.expected.ir.msl
@@ -1,6 +1,6 @@
 SKIP: FAILED
 
-<dawn>/src/tint/lang/msl/writer/printer/printer.cc:355 internal compiler error: %b1 = block {  # root
+<dawn>/src/tint/lang/msl/writer/printer/printer.cc:469 internal compiler error: %b1 = block {  # root
   %arg_0:ptr<handle, texture_storage_2d_array<rg32float, read>, read> = var @binding_point(1, 0)
   %prevent_dce:ptr<storage, vec4<f32>, read_write> = var @binding_point(2, 0)
 }