[clang] [APINotes] Support nested tags (PR #99655)

[Saleem Abdulrasool via cfe-commits]

================
@@ -456,6 +458,7 @@ template <> struct MappingTraits<Tag> {
     IO.mapOptional("EnumKind", T.EnumConvenienceKind);
     IO.mapOptional("SwiftCopyable", T.SwiftCopyable);
     IO.mapOptional("Methods", T.Methods);
+    IO.mapOptional("Tags", T.Tags);
----------------
compnerd wrote:

Hmm, but is it the full set of tags or the tags that have associated attributes? I think that I got confused due to the namespace being built the obvious front to end.

https://github.com/llvm/llvm-project/pull/99655