[clang] [Clang][C++26] Implement Pack Indexing (P2662R3). (PR #72644)

[Erich Keane via cfe-commits]

================
@@ -836,6 +836,8 @@ ANNOTATION(primary_expr) // annotation for a primary expression, used when
                          // message send
 ANNOTATION(decltype)     // annotation for a decltype expression,
                          // e.g., "decltype(foo.bar())"
+ANNOTATION(indexed_pack_type) // annotation for an indexed pack of type,
----------------
erichkeane wrote:

```suggestion
ANNOTATION(pack_indexing_type) // annotation for an indexed pack of type,
```

Does this make sense?  Seems odd that we changed how this is referred to all of a sudden.

https://github.com/llvm/llvm-project/pull/72644