[clang] [Clang] Emit a diagnostic note at the class declaration when the method definition does not match any declaration. (PR #110638)

[Vlad Serebrennikov via cfe-commits]

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@@ -108,6 +108,7 @@ namespace MultilevelSpecialization {
   template<> template<int a, int b>
     void B<int, int>::f(int i, int (&arr1)[a], int (&arr2)[b]) {}
     // since-cxx11-error at -1 {{out-of-line definition of 'f' does not match any declaration in 'cwg2233::MultilevelSpecialization::B<int, int>'}}
+    // expected-note at -6 {{defined here}}
----------------
Endilll wrote:

```suggestion
    //   expected-note@#cwg2233-blah {{defined here}}
```
We shouldn't make the readers count lines to understand, which line the diagnostic is emitted for. Use bookmarks instead (with a proper name, see other tests for the reference).

https://github.com/llvm/llvm-project/pull/110638