Add Request/Response sample with activity-based responses (fixes #6)

[barmoshe]

What was changed

• Added a new sample directory reqrespactivity to the repository.
• Ported the Request/Response demo from Go to Python, which demonstrates how to send a request (via a signal) to a workflow and receive a response via a callback activity.
• This sample includes:
  • workflow.py: Contains the workflow definition, data models, and the uppercase activity.
  • requester.py: Implements a requester that signals the workflow and awaits the callback response.
  • starter.py: Starts the workflow.
  • worker.py: Runs the workflow and activity worker.
  • requester_run.py: Continuously sends requests (e.g., "foo0", "foo1", etc.) to the workflow and prints the uppercase responses.
• An updated README (README.md) provides detailed instructions on running the sample.

Why?

• To provide a Python port of the Request/Response demo as seen in the Go samples.
• This sample demonstrates the use of Temporal's Python SDK for activity-based responses where the workflow processes signal-based requests and responds using a callback activity.
• The implementation serves as a reference for users looking to integrate similar functionality in their Python applications.

Checklist

1. Closes #6 and #7
2. How was this tested:
   • A Temporal server was run locally using Docker.
   • The worker was started via python worker.py to register the workflow and activity.
   • The workflow was started using python starter.py and confirmed to be running.
   • The requester was executed using python requester_run.py, which sent requests (e.g., "foo0", "foo1", etc.) and received correct uppercase responses ("FOO0", "FOO1", etc.).
3. Any docs updates needed?
   • The new sample includes its own README that documents the sample and mirrors the instructions from the Go version.
   • No further updates to docs.temporal.io are required at this time.

[CLAassistant]

All committers have signed the CLA.

[cretz]

#6 and the Go samples predate Workflow Update. We now recommend using workflow update for request/response instead of the "response activity" pattern.