Add generated Q Business client and integration tests

[Alan4506]

Description of changes:

This PR adds integration tests for the Q Business service client (aws-sdk-qbusiness), covering the following:

• Non-streaming operations: create_application, get_application, delete_application, create_index, get_index, create_retriever, get_retriever, chat_sync.
• Bidirectional event streaming operation: chat.

The test structure and patterns follow the same conventions established in the Lex Runtime V2 integration tests (PR #51), such as session-scoped conftest fixtures for resource setup/teardown.

To successfully run the tests locally, follow the steps below:

# Set up your AWS credentials, then:
cd <path-to-smithy-python>
git checkout develop && git pull
make build-py

# Set up and run Q Business integration tests
cd <path-to-aws-sdk-python>/clients/aws-sdk-qbusiness
uv venv .venv && source .venv/bin/activate
uv pip install --group test -e . 
python -m pytest tests/integration

All tests should pass.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[jonathan343]

Thanks @Alan4506!

Left some very minor comments above. All tests succeed for me locally.
I'm fine approving once the commends are addressed.

[jonathan343]

LGTM! Thanks!