Add end-to-end corpus from Tint SPIR-V Reader

Add the unit tests samples from src/reader/spirv when:
- they are valid for Vulkan 1.0 (plus some common extensions)
- they should translate to valid WGSL

Bug: tint:1043
Change-Id: I40a01990dbc40aff5cf7ace0b1aabfd0e437f638
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/60000
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: David Neto <dneto@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>

test/unittest/reader/spirv/SpvBinaryArithTestBasic_SDiv_Vector_UnsignedResult.spvasm.expected.wgsl

@@ -0,0 +1,9 @@
+fn main_1() {
+  let x_1 : vec2<u32> = bitcast<vec2<u32>>((vec2<i32>(30, 40) / vec2<i32>(40, 30)));
+  return;
+}
+
+[[stage(fragment)]]
+fn main() {
+  main_1();
+}