Ractor version 0.7.2 adds support for instant spawning!

This release adds support for spawning actors "instantly" in that we don't wait on the pre_start routine. This is helpful if you want to immediately have access to the ActorRef<TActor> so you can begin sending messages to it without blocking on the pre_start routine.

However if the pre_start fails for any reason, it won't be captured unless the specific join handle is handled manually to monitor the spawning error. Internal documentation is updated to reflect this. Additionally since this is a specialized feature, the functionality is not supported directly on the Actor trait, but only with usage of the ActorRuntime directly.

Additionally we're adding a small auto-implementation for types which implement BytesSerializable such that they are automatically implementing ractor::Message and can be network-sent. This makes most of the built-in numeric types, (), Strings, and vectors of such able to directly used as message types in a cluster context.