[clang] [clang][AST] Add 'IgnoreTemplateParmDepth' to structural equivalence cache (PR #115518)

[Donát Nagy via cfe-commits]

================
@@ -2303,7 +2303,8 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
 
   // Check whether we already know that these two declarations are not
   // structurally equivalent.
-  if (Context.NonEquivalentDecls.count(P))
+  if (Context.NonEquivalentDecls.count(
+          std::make_tuple(D1, D2, Context.IgnoreTemplateParmDepth)))
----------------
NagyDonat wrote:

```suggestion
  if (Context.NonEquivalentDecls[Context.IgnoreTemplateParmDepth].count(P))
```

https://github.com/llvm/llvm-project/pull/115518