[clang] [CIR] Preserve annotate attributes on record declarations (PR #207551)

[via cfe-commits]

================
@@ -48,6 +48,12 @@ struct StructTypeStorage : public mlir::TypeStorage {
   bool padded;
   bool is_class;
 
+  // Annotations are payload set at completion (like members/layout), not part
+  // of the type's identity: named records are uniqued by name, so there is at
+  // most one annotation set per type. Keeping them out of the key is also
+  // required so an incomplete record can be completed in place.
----------------
RedNicStone wrote:

```diff
+  // Array of #cir.annotation attributes, set at completion (like
+  // members/layout), not part of the type's identity: named records are
+  // uniqued by name, so there is at most one annotation set per type. Keeping
+  // them out of the key is also required so an incomplete record can be
+  // completed in place.
```
Sounds good. Would this do the job?

https://github.com/llvm/llvm-project/pull/207551