[Runtime] Fix _swift_refCountBytesForMetatype for reference types
_swift_addRefCountStringForMetatype and _swift_refCountBytesForMetatype diverged in the code that determines whether a type is a reference, causing the size number of ref count bytes to differ from the actually used bytes. This can cause early termination of the runtime interpreter functions, which in turn causes unbalanced reference counts.
rdar://112474091
