[tint] Add RW storage textureStore overloads

Adds them to the intrinsics table but no codegen support yet.

Bug: tint:2007
Change-Id: Ie909b9bf1557f69a4adde6ab2a9ff8646b9ce53f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/146240
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>
diff --git a/test/tint/builtins/gen/literal/textureStore/8a46ff.wgsl.expected.glsl b/test/tint/builtins/gen/literal/textureStore/8a46ff.wgsl.expected.glsl
new file mode 100644
index 0000000..566c250
--- /dev/null
+++ b/test/tint/builtins/gen/literal/textureStore/8a46ff.wgsl.expected.glsl
@@ -0,0 +1,52 @@
+#version 310 es
+
+layout(rgba16f) uniform highp writeonly image2D arg_0;
+void textureStore_8a46ff() {
+  imageStore(arg_0, ivec2(1), vec4(1.0f));
+}
+
+vec4 vertex_main() {
+  textureStore_8a46ff();
+  return vec4(0.0f);
+}
+
+void main() {
+  gl_PointSize = 1.0;
+  vec4 inner_result = vertex_main();
+  gl_Position = inner_result;
+  gl_Position.y = -(gl_Position.y);
+  gl_Position.z = ((2.0f * gl_Position.z) - gl_Position.w);
+  return;
+}
+#version 310 es
+precision highp float;
+
+layout(rgba16f) uniform highp writeonly image2D arg_0;
+void textureStore_8a46ff() {
+  imageStore(arg_0, ivec2(1), vec4(1.0f));
+}
+
+void fragment_main() {
+  textureStore_8a46ff();
+}
+
+void main() {
+  fragment_main();
+  return;
+}
+#version 310 es
+
+layout(rgba16f) uniform highp writeonly image2D arg_0;
+void textureStore_8a46ff() {
+  imageStore(arg_0, ivec2(1), vec4(1.0f));
+}
+
+void compute_main() {
+  textureStore_8a46ff();
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  compute_main();
+  return;
+}