To determine whether an instruction may require pack metadata, the types
of its operands are examined.
Previously, the top level type was checked for having a pack in its
signature, and the whole type was checked for having a type anywhere in
its layout (via TypeLowering). This didn't account for the case where
the metadata was required for a resilient type which uses a pack in its
signature.
Here, during type lowering, a type having a pack in its signature is
counted towards the type having a pack.
Fixes a compiler crash.
rdar://147207926
