Memleak for PAQs with more than four shader stages

Description
When declaring a payload struct with PAQs, memory leaks if one of the PAQ clauses specifies more than four shader stages.
This is because the hlsl::PayloadAccessAnnotation keeps those stages in a llvm::SmallVector<hlsl::DXIL::PayloadAccessShaderStage, 4u> field, which starts allocating memory in this case. Since UnusualAnnotation has no virtual deconstructor this memory is never free'd.

Steps to Reproduce

1. Create a dxc Release build on Linux with Clang 18 + Asan enabled (asan only reported the leak in this specific configuration).
2. Create an hlsl file with a payload struct. One of the payload fields needs to have more than four shader stages, eg:

struct [raypayload] Payload
{
     float elem
          : write(caller,closesthit,anyhit,closesthit,miss)
          : read(caller,closesthit,anyhit,closesthit,miss);
          : write(caller,anyhit,closesthit,miss)
          : read(caller,anyhit,closesthit,miss);
};

Actual Behavior
This was observed in a CI run for https://github.com/microsoft/DirectXShaderCompiler/pull/7097 (commit https://github.com/microsoft/DirectXShaderCompiler/pull/7097/commits/cb132036cfa5ea01283af5de6b8ecea15c141ac6). The test case in this PR has since been fixed to only specify four stages to workaround this issue.

******************** TEST 'Clang :: SemaHLSL/hlsl/objects/HitObject/hitobject-entry-errors.hlsl' FAILED ********************
Script:
--
/home/vsts/work/1/s/build/./bin/dxc -T lib_6_9 /home/vsts/work/1/s/tools/clang/test/SemaHLSL/hlsl/objects/HitObject/hitobject-entry-errors.hlsl -verify
--
Exit Code: 1

Command Output (stderr):
--

=================================================================
==18293==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 72 byte(s) in 2 object(s) allocated from:
    #0 0x55a3223affbd in operator new[](unsigned long) (/home/vsts/work/1/s/build/bin/dxc-3.7+0x203fbd) (BuildId: 34f0a07c804d72cd)
    #1 0x7f129b11d3b6 in llvm::SmallVectorBase::grow_pod(void*, unsigned long, unsigned long) /home/vsts/work/1/s/lib/Support/SmallVector.cpp:27:19
    #2 0x7f129ce097f5 in grow_pod /home/vsts/work/1/s/include/llvm/ADT/SmallVector.h:81:22
    #3 0x7f129ce097f5 in grow /home/vsts/work/1/s/include/llvm/ADT/SmallVector.h:327:11
    #4 0x7f129ce097f5 in llvm::SmallVectorImpl<hlsl::DXIL::PayloadAccessShaderStage>::operator=(llvm::SmallVectorImpl<hlsl::DXIL::PayloadAccessShaderStage> const&) /home/vsts/work/1/s/include/llvm/ADT/SmallVector.h:763:11
    #5 0x7f129cdd88d2 in SmallVector /home/vsts/work/1/s/include/llvm/ADT/SmallVector.h:894:27
    #6 0x7f129cdd88d2 in PayloadAccessAnnotation /home/vsts/work/1/s/tools/clang/include/clang/AST/HlslTypes.h:282:8
    #7 0x7f129cdd88d2 in clang::Parser::MaybeParseHLSLAttributes(std::__1::vector<hlsl::UnusualAnnotation*, std::__1::allocator<hlsl::UnusualAnnotation*>>&) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDecl.cpp:418:38
    #8 0x7f129cdff895 in MaybeParseHLSLAttributes /home/vsts/work/1/s/tools/clang/include/clang/Parse/Parser.h:2102:12
    #9 0x7f129cdff895 in clang::Parser::ParseDirectDeclarator(clang::Declarator&) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDecl.cpp:6315:9
    #10 0x7f129cdfcfe9 in clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void (clang::Parser::*)(clang::Declarator&)) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDecl.cpp:5903:7
    #11 0x7f129ce20015 in clang::Parser::ParseCXXMemberDeclaratorBeforeInitializer(clang::Declarator&, clang::VirtSpecifiers&, clang::ActionResult<clang::Expr*, true>&, clang::Parser::LateParsedAttrList&) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDeclCXX.cpp:2107:5
    #12 0x7f129ce236cc in clang::Parser::ParseCXXClassMemberDeclaration(clang::AccessSpecifier, clang::AttributeList*, clang::Parser::ParsedTemplateInfo const&, clang::ParsingDeclRAIIObject*) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDeclCXX.cpp:2489:7
    #13 0x7f129ce1cf24 in clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::Parser::ParsedAttributesWithRange&, unsigned int, clang::Decl*) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDeclCXX.cpp:3153:7
    #14 0x7f129ce18816 in clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::Parser::ParsedAttributesWithRange&) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDeclCXX.cpp:1786:7
    #15 0x7f129cde4876 in clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseDecl.cpp:4151:7
    #16 0x7f129cd88700 in clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier) /home/vsts/work/1/s/tools/clang/lib/Parse/Parser.cpp:908:3
    #17 0x7f129cd882d7 in clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) /home/vsts/work/1/s/tools/clang/lib/Parse/Parser.cpp:981:12
    #18 0x7f129cd87368 in clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) /home/vsts/work/1/s/tools/clang/lib/Parse/Parser.cpp:839:12
    #19 0x7f129cd86cf7 in clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&) /home/vsts/work/1/s/tools/clang/lib/Parse/Parser.cpp:606:12
    #20 0x7f129cce8da7 in clang::ParseAST(clang::Sema&, bool, bool) /home/vsts/work/1/s/tools/clang/lib/Parse/ParseAST.cpp:140:11
    #21 0x7f129b75b50d in clang::FrontendAction::Execute() /home/vsts/work/1/s/tools/clang/lib/Frontend/FrontendAction.cpp:455:8
    #22 0x7f129a1b9959 in DxcCompiler::Compile(DxcBuffer const*, wchar_t const**, unsigned int, IDxcIncludeHandler*, _GUID const&, void**) /home/vsts/work/1/s/tools/clang/tools/dxcompiler/dxcompilerobj.cpp:933:18
    #23 0x7f129a1b005c in hlsl::DxcCompilerAdapter::WrapCompile(bool, IDxcBlob*, wchar_t const*, wchar_t const*, wchar_t const*, wchar_t const**, unsigned int, DxcDefine const*, unsigned int, IDxcIncludeHandler*, IDxcOperationResult**, wchar_t**, IDxcBlob**) /home/vsts/work/1/s/tools/clang/tools/dxcompiler/dxcompilerobj.cpp:1855:5
    #24 0x7f129a1b2e2c in hlsl::DxcCompilerAdapter::CompileWithDebug(IDxcBlob*, wchar_t const*, wchar_t const*, wchar_t const*, wchar_t const**, unsigned int, DxcDefine const*, unsigned int, IDxcIncludeHandler*, IDxcOperationResult**, wchar_t**, IDxcBlob**) /home/vsts/work/1/s/tools/clang/tools/dxcompiler/dxcompilerobj.cpp:1758:10
    #25 0x7f129a1b47c8 in hlsl::DxcCompilerAdapter::Compile(IDxcBlob*, wchar_t const*, wchar_t const*, wchar_t const*, wchar_t const**, unsigned int, DxcDefine const*, unsigned int, IDxcIncludeHandler*, IDxcOperationResult**) /home/vsts/work/1/s/tools/clang/tools/dxcompiler/dxcompileradapter.h:75:12
    #26 0x55a3223c0d06 in DxcContext::Compile() /home/vsts/work/1/s/tools/clang/tools/dxclib/dxc.cpp:874:9
    #27 0x55a3223c9fd4 in dxc::main(int, char const**) /home/vsts/work/1/s/tools/clang/tools/dxclib/dxc.cpp:1502:24
    #28 0x7f1298629d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 490fef8403240c91833978d494d39e537409b92e)

SUMMARY: AddressSanitizer: 72 byte(s) leaked in 2 allocation(s).

Environment
Observed with

• DXC top of tree
• Azure CI Clang /Release/linux pipeline. Reproduced locally using Ubuntu on WSL / Clang 18.1.3 / Release build with cmake -DLLVM_USE_SANITIZER=Address

Start in tools/clang/include/clang/AST/HlslTypes.h, where PayloadAccessAnnotation and UnusualAnnotation are defined, then inspect their allocation and cleanup through tools/clang/lib/Parse/ParseDecl.cpp. Reproduce with the payload containing more than four shader stages using a Release Linux build with Clang 18 and AddressSanitizer. Done means the reproducer no longer reports a leak.