Allow getting type of ScriptObject (#99542)
Summary:
A very old refactor (https://github.com/pytorch/pytorch/pull/29500) split ScriptModule into ScriptObject (base class) and ScriptModule (subclass). When moving methods around, the `_type` method was moved from ScriptModule to ScriptObject, but the type of its argument wasn't changed. Therefore, it is now impossible to invoke `_type` on a ScriptObject.
The reason I need this fix is that I am using PyTorch's dispatch mode to intercept some operators that accept/return custom classes, which end up being encoded as ScriptObject, and in order to properly handle them I need to be able to verify their type.
Test Plan: N/A
Differential Revision: D45118675
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99542
Approved by: https://github.com/albanD
