tint: Add support for atomic ops to spirv reader

The following operations are supported:

OpAtomicLoad
OpAtomicStore
OpAtomicExchange
OpAtomicCompareExchange
OpAtomicCompareExchangeWeak
OpAtomicIIncrement
OpAtomicIDecrement
OpAtomicIAdd
OpAtomicISub
OpAtomicSMin
OpAtomicUMin
OpAtomicSMax
OpAtomicUMax
OpAtomicAnd
OpAtomicOr
OpAtomicXor

These are not, but may be supported in the future:

OpAtomicFlagTestAndSet
OpAtomicFlagClear
OpAtomicFMinEXT
OpAtomicFMaxEXT
OpAtomicFAddEXT

Bug: tint:1441
Change-Id: Ifd53643b38d43664905a0dddfca609add4914670
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/94121
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>

test/tint/builtins/atomicStore/array/array.spvasm.expected.glsl

@@ -0,0 +1,39 @@
+#version 310 es
+
+uint local_invocation_index_1 = 0u;
+shared uint wg[4];
+void compute_main_inner(uint local_invocation_index) {
+  uint idx = 0u;
+  idx = local_invocation_index;
+  {
+    for(; !(!((idx < 4u))); idx = (idx + 1u)) {
+      atomicExchange(wg[idx], 0u);
+    }
+  }
+  barrier();
+  atomicExchange(wg[1], 1u);
+  return;
+}
+
+void compute_main_1() {
+  compute_main_inner(local_invocation_index_1);
+  return;
+}
+
+void compute_main(uint local_invocation_index_1_param) {
+  {
+    for(uint idx_1 = local_invocation_index_1_param; (idx_1 < 4u); idx_1 = (idx_1 + 1u)) {
+      uint i = idx_1;
+      atomicExchange(wg[i], 0u);
+    }
+  }
+  barrier();
+  local_invocation_index_1 = local_invocation_index_1_param;
+  compute_main_1();
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  compute_main(gl_LocalInvocationIndex);
+  return;
+}