Enable CodeGenHashStability tests by default on all platforms (#5548)

On my local machine the CodeGenHashStability test takes 15 seconds to
run. While that is longer than the entire rest of the test suite, it
makes the full test suite run only take 17 seconds, which is still
reasonable.

This change then goes a step further and breaks up the
CodeGenHashStability test into multiple smaller tests. With that
refactoring the full test suite drops from 17s to 10s. The end result is
that enabling CodeGenHashStability costs only 1s on Release+Aserts
builds.

Here is a rough breakdown of the performance impact of this change on
test time for the full test suite:

```
┌───────────────┬───────────────┬───────────────┐
│               │Release+Asserts│ Debug+Asserts │
├───────────────┼───────────────┼───────────────┤
│ Before        │      9s       │      57s      │
├───────────────┼───────────────┼───────────────┤
│ After         │     10s       │      88s      │
└───────────────┴───────────────┴───────────────┘
```

We should enable this test case by default and evaluate ways to better
parallelize this test so that so that we can run it more efficiently.

tools/clang/unittests/HLSL/CompilerTest.cpp

@@ -254,16 +254,22 @@ class CompilerTest : public ::testing::Test {
   TEST_METHOD(BatchValidation)
   TEST_METHOD(BatchPIX)
 
+  TEST_METHOD(CodeGenHashStabilityD3DReflect)
+  TEST_METHOD(CodeGenHashStabilityDisassembler)
+  TEST_METHOD(CodeGenHashStabilityDXIL)
+  TEST_METHOD(CodeGenHashStabilityHLSL)
+  TEST_METHOD(CodeGenHashStabilityInfra)
+  TEST_METHOD(CodeGenHashStabilityPIX)
+  TEST_METHOD(CodeGenHashStabilityRewriter)
+  TEST_METHOD(CodeGenHashStabilitySamples)
+  TEST_METHOD(CodeGenHashStabilityShaderTargets)
+  TEST_METHOD(CodeGenHashStabilityValidation)
+
   TEST_METHOD(SubobjectCodeGenErrors)
   BEGIN_TEST_METHOD(ManualFileCheckTest)
     TEST_METHOD_PROPERTY(L"Ignore", L"true")
   END_TEST_METHOD()
 
-  // Batch directories
-  BEGIN_TEST_METHOD(CodeGenHashStability)
-      TEST_METHOD_PROPERTY(L"Priority", L"2")
-  END_TEST_METHOD()
-
   dxc::DxcDllSupport m_dllSupport;
   VersionSupportInfo m_ver;
 
@@ -2454,7 +2460,6 @@ TEST_F(CompilerTest, CompileWithRootSignatureThenStripRootSignature) {
   VERIFY_IS_NOT_NULL(pPartHeader);
 }
 
-#if _WIN32 // API -setrootsignature requires reflection, which isn't supported on non-win
 TEST_F(CompilerTest, CompileThenSetRootSignatureThenValidate) {
   CComPtr<IDxcCompiler> pCompiler;
   VERIFY_SUCCEEDED(CreateCompiler(&pCompiler));
@@ -2589,7 +2594,7 @@ TEST_F(CompilerTest, CompileThenSetRootSignatureThenValidate) {
                              pRSBlobReplace->GetBufferPointer(),
                              pRSBlob->GetBufferSize()));
 }
-#endif // _WIN32 - API -setrootsignature requires reflection, which isn't supported on non-win
+
 TEST_F(CompilerTest, CompileSetPrivateThenWithStripPrivate) {
   CComPtr<IDxcCompiler> pCompiler;
   CComPtr<IDxcOperationResult> pResult;
@@ -4271,13 +4276,44 @@ TEST_F(CompilerTest, DISABLED_ManualFileCheckTest) {
   }
 }
 
+TEST_F(CompilerTest, CodeGenHashStabilityD3DReflect) {
+  CodeGenTestCheckBatchHash(L"d3dreflect");
+}
 
-#ifdef _WIN32
-TEST_F(CompilerTest, CodeGenHashStability) {
-#else
-TEST_F(CompilerTest, DISABLED_CodeGenHashStability) {
-#endif
-  CodeGenTestCheckBatchHash(L"");
+TEST_F(CompilerTest, CodeGenHashStabilityDisassembler) {
+  CodeGenTestCheckBatchHash(L"disassembler");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityDXIL) {
+  CodeGenTestCheckBatchHash(L"dxil");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityHLSL) {
+  CodeGenTestCheckBatchHash(L"hlsl");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityInfra) {
+  CodeGenTestCheckBatchHash(L"infra");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityPIX) {
+  CodeGenTestCheckBatchHash(L"pix");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityRewriter) {
+  CodeGenTestCheckBatchHash(L"rewriter");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilitySamples) {
+  CodeGenTestCheckBatchHash(L"samples");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityShaderTargets) {
+  CodeGenTestCheckBatchHash(L"shader_targets");
+}
+
+TEST_F(CompilerTest, CodeGenHashStabilityValidation) {
+  CodeGenTestCheckBatchHash(L"validation");
 }
 
 TEST_F(CompilerTest, BatchD3DReflect) {