Python: Add support for the MagenticWorkflowBuilder (#496)
* magentic happy path - wip
* Support workflow high-level magentic builder API. Add tests and samples.
* Add sample docstring
* Addressing PR feedback round 1
* Fix mypy errors
* Callback improvements
* Rename to MagenticBuilder
* Improvements
* Emit function calling deltas
* PR feedback 2
* Clean up sample
Evan Mattson