[Feature Request] Enable Eager Workflow Start #606
Description
Is your feature request related to a problem? Please describe.
Support for Eager Workflow Start has been enabled by the server since 1.20, and is already available in Java and Go SDKs. It reduces latency to start a new workflow by allowing the client to directly schedule a first task to a local worker, bypassing matching and an extra transaction/roundtrip. See temporalio/features#242 for details.
We want to support Eager Workflow Start for core-based languages, starting with Python.
Describe the solution you'd like
The implementation relies on #605, a worker registry that finds local compatible workers,
and extends it with a SlotManager trait that provides a method to reserve a worker slot, and another one to schedule a task using this slot.
The client will also transparently use eager mode when it is enabled, and gracefully default to non-eager mode when either the server or the SlotManager rejects it.