New Get-Info / Get-Result / long-poll design (temporalio#673)

Two APIs:

1. **Return Info, optionally waiting for next state change before doing
so**
In addition to Info it returns a long-poll token. Optionally accepts a
long-poll token, meaning "wait for next state change and then return
latest info". Optionally includes outcome and input in response.
1. **Long-poll for outcome**

Author: dandavison