[clang-repl][ASTMatcher] Failed template instantiation leaves orphan lambda closure declarations

Reproducer:

```cpp
template struct O : A, B {};

template void f() {
auto a = [] {};
auto b = [] {};
O(a, b)();
}

template void f();
```

With an assertion-enabled build:

```console
./build/bin/clang-query -c='match classTemplateSpecializationDecl(hasAnyTemplateArgument(refersToType(recordType(hasDeclaration(cxxRecordDecl(hasAncestor(translationUnitDecl())))))))' repro.cpp -- -std=c++20
```

Crashes with:

```
Parent map should be complete!
UNREACHABLE executed at /llvm-project/clang/lib/ASTMatchers/ASTMatchFinder.cpp:1221!
```

Start with the repro.cpp template-instantiation example and run the provided clang-query command against an assertion-enabled build. Read clang/lib/ASTMatchers/ASTMatchFinder.cpp around line 1221 to trace why the parent map is incomplete after the failed instantiation. Done means the reproducer no longer triggers the assertion and regression coverage protects the fix.

Written by the indexing model from the issue text.