Generate LLC for Question Answering authoring client

[heaths]

Now that inference has GA'd, we need to produce the authoring client for Question Answering.

• [ ] Generate QuestionAnsweringProjectClient in a subnamespace e.g., Azure.AI.Language.QuestionAnswering.Project (exact name TBD).
  • In .NET's autorest.md, there's already a batch section commented out you can use. Just set the namespace separately, and also disable putting models in a separate namespace, which archboard for .NET wants by default.
• [ ] Add champion scenario(s) to README.md
• [ ] Add additional authoring samples to samples/ directory.
• [ ] Update documentation including MigrationGuide.md as needed.
• [ ] Add/record tests with suitable code coverage.

[heaths]

Be sure to integrate @kristapratico's changes to autorest.md from Azure/azure-sdk-for-python#26308