[RPC] Use qualified name str directly in RPC torch script code path (#34733)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34733
simplify
ghstack-source-id: 100292435
Test Plan:
```
buck test mode/dev-nosan //caffe2/test/distributed/rpc:rpc_fork
```
```
buck test mode/dev-nosan //caffe2/test/distributed/rpc/jit:rpc_fork
buck build mode/dev-nosan //caffe2/test/distributed/rpc/jit:rpc_fork \
&& buck-out/gen/caffe2/test/distributed/rpc/jit/rpc_fork\#binary.par \
-r test_return_local_script_class_rref_in_py_and_use_in_script
buck build mode/dev-nosan //caffe2/test/distributed/rpc/jit:rpc_fork \
&& buck-out/gen/caffe2/test/distributed/rpc/jit/rpc_fork\#binary.par \
-r test_return_local_script_module_rref_in_py_and_use_in_script
```
Differential Revision: D20442573
fbshipit-source-id: 87f8b7d94adc03544f8e2955d01cd4702bb31a34
