[WebPubSubClient] Convert azure-messaging-webpubsubclient package from setup.py to pyproject.toml

[swathipil]

Convert azure-messaging-webpubsubclient from using setup.py to pyproject.toml. Avoid converting azure-mgmt* packages.

1. As an example, take a look at the conversion of azure-eventhub setup.py to pyproject.toml.
2. Ensure that the dynamic version file path is added correctly.
3. Ensure that the correct 'requires-python >=' Python version is correct.
4. Ensure that the project.urls repository is ""https://github.com/Azure/azure-sdk-for-python.""
5. Ensure the py.typed line looks like:
   pytyped = ["py.typed"]
6. If stress/ or doc/ folders exist at the project root dir, exclude them.