This allows external tools to locate the metadata pointer without needing to call the accessor function.
This is only useful for non-generic types, so we borrow the HasCanonicalMetadataPrespecializations flag to indicate the presence of this pointer on non-generic types, and it continues to indicate the presence of prespecializations for generic types.
Only emit this pointer for internal/private types with no runtime initialization. Public type metadata can be found with the symbol, and it's not useful for types that require runtime initialization.
