[clang] Assertion `SS.isSet() && "C++ scope was cleared ?"' failed in -fms-compatibility mode

similar (but already closed) issue: https://github.com/llvm/llvm-project/issues/206992 https://github.com/llvm/llvm-project/issues/207498

Note: using `-fms-compatibility`

Reproducer:
https://godbolt.org/z/dh3e4rh5Y
```cpp
template struct S {};

template template void S::foo() {
void S::foo();
}
```

Backtrace:
```console
clang++: /root/llvm-project/llvm/tools/clang/include/clang/Parse/Parser.h:2593: clang::Parser::DeclaratorScopeObj::~DeclaratorScopeObj(): Assertion `SS.isSet() && "C++ scope was cleared ?"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and dumped files.
Stack dump:
0. Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -fms-compatibility
1. :4:26: current parser token ';'
2. :3:62: parsing function body 'S::foo'
3. :3:62: in compound statement ('{}')
#0 0x000000000439e6c8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x439e6c8)
#1 0x000000000439b584 llvm::sys::RunSignalHandlers() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x439b584)
#2 0x000000000439bbac llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x439bbac)
#3 0x00000000042dabf8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
#4 0x00007791e6c45330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
#5 0x00007791e6c9eb2c pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x9eb2c)
#6 0x00007791e6c4527e raise (/lib/x86_64-linux-gnu/libc.so.6+0x4527e)
#7 0x00007791e6c288ff abort (/lib/x86_64-linux-gnu/libc.so.6+0x288ff)
#8 0x00007791e6c2881b (/lib/x86_64-linux-gnu/libc.so.6+0x2881b)
#9 0x00007791e6c3b517 (/lib/x86_64-linux-gnu/libc.so.6+0x3b517)
#10 0x0000000006cdd0b4 clang::Parser::ParseDirectDeclarator(clang::Declarator&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cdd0b4)
#11 0x0000000006cc4602 clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void (clang::Parser::*)(clang::Declarator&)) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cc4602)
#12 0x000000000877f2e1 clang::StackExhaustionHandler::runWithSufficientStackSpace(clang::SourceLocation, llvm::function_ref) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x877f2e1)
#13 0x0000000006cdd767 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cdd767)
#14 0x0000000006cdf28f clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, bool, clang::Parser::ForRangeInit*, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cdf28f)
#15 0x0000000006cdf75c clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cdf75c)
#16 0x0000000006d8d42d clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::LabelDecl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6d8d42d)
#17 0x0000000006d8dcd9 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::LabelDecl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6d8dcd9)
#18 0x0000000006d96215 clang::Parser::ParseCompoundStatementBody(bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6d96215)
#19 0x0000000006d96a5a clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6d96a5a)
#20 0x0000000006c94fc3 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::LateParsedAttrList*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6c94fc3)
#21 0x0000000006cde8d6 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cde8d6)
#22 0x0000000006da25e0 clang::Parser::ParseDeclarationAfterTemplate(clang::DeclaratorContext, clang::Parser::ParsedTemplateInfo&, clang::ParsingDeclRAIIObject&, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6da25e0)
#23 0x0000000006daec73 clang::Parser::ParseTemplateDeclarationOrSpecialization(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::AccessSpecifier) (.part.0) ParseTemplate.cpp:0:0
#24 0x0000000006daf06a clang::Parser::ParseDeclarationStartingWithTemplate(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6daf06a)
#25 0x0000000006cdf900 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::ParsedAttributes&, clang::ParsedAttributes&, clang::SourceLocation*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6cdf900)
#26 0x0000000006c96446 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6c96446)
#27 0x0000000006c97335 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6c97335)
#28 0x0000000006c7422a clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6c7422a)
#29 0x0000000004e992c8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4e992c8)
#30 0x00000000051c4098 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x51c4098)
#31 0x0000000005151dad clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5151dad)
#32 0x000000000529c7cd clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x529c7cd)
#33 0x0000000000db774c cc1_main(llvm::ArrayRef, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdb774c)
#34 0x0000000000dae35a ExecuteCC1Tool(llvm::SmallVectorImpl&, llvm::ToolContext const&, llvm::IntrusiveRefCntPtr) driver.cpp:0:0
#35 0x0000000000dae4dd int llvm::function_ref&)>::callback_fn&)>(long, llvm::SmallVectorImpl&) driver.cpp:0:0
#36 0x0000000004f104b9 void llvm::function_ref::callback_fn>, std::__cxx11::basic_string, std::allocator>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#37 0x00000000042db034 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x42db034)
#38 0x0000000004f11025 clang::driver::CC1Command::Execute(llvm::ArrayRef>, std::__cxx11::basic_string, std::allocator>*, bool*) const (.part.0) Job.cpp:0:0
#39 0x0000000004ec9ad2 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4ec9ad2)
#40 0x0000000004ece307 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4ece307)
#41 0x0000000004ed87f5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4ed87f5)
#42 0x0000000000db3c3a clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdb3c3a)
#43 0x0000000000ccff2a main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xccff2a)
#44 0x00007791e6c2a1ca (/lib/x86_64-linux-gnu/libc.so.6+0x2a1ca)
#45 0x00007791e6c2a28b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28b)
#46 0x0000000000dadd05 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdadd05)
clang++: error: clang frontend command failed due to signal (use -v to see invocation)
Compiler returned: 134
```

Reproduce the assertion with the provided C++ example and -fms-compatibility, then start in clang/include/clang/Parse/Parser.h and follow ParseDirectDeclarator in the stack trace. Trace how the nested template declaration affects the C++ scope and verify that the reproducer no longer aborts after the fix.

Written by the indexing model from the issue text.