[JIT] constant object compilation unit ref fix (#65442)
Summary:
// A non owning pointer to a type. When a class get inserted as a constant
// into a graph, if we used a strong pointer we would have a circular reference
// from Object -> CompilationUnit and CompilationUnit -> Graph (which owns the
// Constant Object)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65442
Reviewed By: ezyang
Differential Revision: D31101962
Pulled By: eellison
fbshipit-source-id: f1c1cfbe5a8d16a832cad7ba46e2a57a98670083
