Add support for spirv1.6

Add command line support which enables the following behavior:

- Remap discard

  Map discard to DemoteToHelperInvocation for HLSL shaders. Map to
  OpTerminateInvocation for GLSL shaders.

- Decorate HelperInvocation with Volatile

- Use localSizeId for execution mode

  WorkGroupSize is deprecated in spirv1.6

Also update known goods to SPIRV 1.6

gtests/Spv.FromFile.cpp

@@ -69,6 +69,7 @@ using CompileVulkanToSpirvDeadCodeElimTest = GlslangTest<::testing::TestWithPara
 using CompileVulkanToDebugSpirvTest = GlslangTest<::testing::TestWithParam<std::string>>;
 using CompileVulkan1_1ToSpirvTest = GlslangTest<::testing::TestWithParam<std::string>>;
 using CompileToSpirv14Test = GlslangTest<::testing::TestWithParam<std::string>>;
+using CompileToSpirv16Test = GlslangTest<::testing::TestWithParam<std::string>>;
 using CompileOpenGLToSpirvTest = GlslangTest<::testing::TestWithParam<std::string>>;
 using VulkanSemantics = GlslangTest<::testing::TestWithParam<std::string>>;
 using OpenGLSemantics = GlslangTest<::testing::TestWithParam<std::string>>;
@@ -122,6 +123,13 @@ TEST_P(CompileToSpirv14Test, FromFile)
                             Target::Spv);
 }
 
+TEST_P(CompileToSpirv16Test, FromFile)
+{
+    loadFileCompileAndCheck(GlobalTestSettings.testRoot, GetParam(),
+                            Source::GLSL, Semantics::Vulkan, glslang::EShTargetUniversal, glslang::EShTargetSpv_1_6,
+                            Target::Spv);
+}
+
 // Compiling GLSL to SPIR-V under OpenGL semantics. Expected to successfully
 // generate SPIR-V.
 TEST_P(CompileOpenGLToSpirvTest, FromFile)
@@ -621,6 +629,18 @@ INSTANTIATE_TEST_SUITE_P(
     FileNameAsCustomTestSuffix
 );
 
+// clang-format off
+INSTANTIATE_TEST_SUITE_P(
+    Glsl, CompileToSpirv16Test,
+    ::testing::ValuesIn(std::vector<std::string>({
+        "spv.1.6.conditionalDiscard.frag",
+        "spv.1.6.helperInvocation.frag",
+        "spv.1.6.specConstant.comp",
+    })),
+    FileNameAsCustomTestSuffix
+);
+
+
 // clang-format off
 INSTANTIATE_TEST_SUITE_P(
     Hlsl, HlslIoMap,