[clang] [Clang] Fix 'counted_by' for nested struct pointers (PR #110497)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

> Yeah so the problem is if you do `__builtin_dynamic_object_size(v, 0)`
> 
> In that case it's a `DeclRefExpr`, a pointer, and an `LValue`.

Can you give a more complete example?  I just tried the following, and I see an lvaluetorvalue cast.

int f(const void *p) { return __builtin_dynamic_object_size(p, 0); }

https://github.com/llvm/llvm-project/pull/110497