Can we lose cloudpickle for spawning? Wait for bootstrap? #131
Description
As per discussion in #128, it's hypothetically possible to drop use of cloudpickle for sending objects/state to spawned subprocs by simply just not doing it until the tractor core machinery / runtime comes up.
As an example instead of sending state to the child process at spawn time we could simply pass all post-runtime required Actor.__init__() data to Actor._async_main() allowing us to just use msgpack and the Actor.load_modules()/Actor._get_rpc_func() named module loading way of invoking the target entrypoint, and pass all pre-runtime required data during the initial handshake.
Very open to discussion and thoughts 😸