[clang] [clang][ASTImporter] skip TemplateTypeParmDecl in VisitTypeAliasTemplateDecl (PR #74919)

[Balázs Kéri via cfe-commits]

balazske wrote:

This code for the loop in `VisitTypeAliasTemplateDecl` should work:
```
    for (auto *FoundDecl : FoundDecls) {
      if (!FoundDecl->isInIdentifierNamespace(IDNS))
        continue;
      if (auto *FoundAlias = dyn_cast<TypeAliasTemplateDecl>(FoundDecl)) {
        if (IsStructuralMatch(D, FoundAlias))
          return Importer.MapImported(D, FoundAlias);

        ConflictingDecls.push_back(FoundDecl);
      }
    }
```

https://github.com/llvm/llvm-project/pull/74919