Adds Workflow Update to Samples

[rachfop]

What was changed

Adds the Workflow Update to the sample's repo.

Why?

Because users will want to see how to use the new Update feature with Python.
Gracefully shut down the worker too.

Checklist

1. Closes

2. How was this tested:

You need the Temporal Python 1.4 or above.
Only works on the local dev server with the config setup.

3. Any docs updates needed?

Once this gets approved - I'll add something similar to the docs (and incorporate any additional feedback).

[cretz]

This is great, thanks!

[cretz]

Looks like you may need to do a poe format. Also, hello/hello_update.py may be a better name than hello/hello_workflow_update.py to match signals, but this is fine too.