support torch script call over rpc (#30063)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30063
This diff makes following changes:
1. Providing a new set of python rpc privated APIs, they can accept an annotated TorchScript call and this call can be serialized, deserialized and executed in C++ without GIL. These privated APIs will be binded to JIT in the future, and they are different from public APIs as future JIT binded private APIs will be able to accept qualified_name, not callables. These private APIs are subject to be deprecated once JIT supports torch script function to be a JIT type.
Also, these APIs require torch script function to be defined and annotated by users in python land, it can not be script class/module constructor or class/module methods.
2. This diff also allows public rpc APIs to accept an annotated TorchScript call and execute code path that above private APIs ran on. Therefore if users invoke an annotated TorchScript call over RPC, this call can be serialized, deserialized and executed in C++ without GIL as well.
3. The above private APIs call a newly defined C++ function to make rpc torch script call to be serialized, deserialized and executed in C++ land. This C++ function returns an ivalue::Future. so that in follow up diff this C++ function can be called when these privated APIs are binded to JIT.
4. script_call.cpp/.h and request_callback_impl.cpp files are refactored accordingly so that torch script call and builtin call can share same message type and codes.
5. refactored deserializeResponse() and added a new utility to deserizalize response to IValue
ghstack-source-id: 96638829
Test Plan: unit test
Differential Revision: D18482934
fbshipit-source-id: bd82a0d820c47a8e45b2e7c616eca06573f7d7ea
