[easy] Refactor MultiOutput. codegen_list_tuple_access to use subclass type checks (#121662)
Summary:
# Why?
Right now I'm running into a case where `itype` is `torch.fx.immutable_collections.immutable_list` which is a subclass of `list`. However, currently we're checking the concrete types (i.e. `list`) and `immutable_list` isn't explictly supported here.
Thus, we use a runtime check that looks at the subclass so we can support subclasses -- such as immutable_list -- as well.
Test Plan: ci
Differential Revision: D54764829
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121662
Approved by: https://github.com/aakhundov
