use hypercorn instead of gunicorn

[pjirsa]

Purpose

Resolves issue #2405 by using hypercorn instead of gunicorn in startup command.

Type of change

[X] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

Code quality checklist

See CONTRIBUTING.md for more details.

• The current tests all pass (python -m pytest).
• I added tests that prove my fix is effective or that my feature works
• I ran python -m pytest --cov to verify 100% coverage of added lines
• I ran python -m mypy to check for type errors
• I either used the pre-commit hooks or ran ruff and black manually on my code.

[pamelafox]

Right now, we use the gunicorn configuration to make sure that logging works and that other settings are properly setup:
https://github.com/Azure-Samples/azure-search-openai-demo/blob/main/app/backend/gunicorn.conf.py

Is everything still working with hypercorn, such as the logging? I have not tested hypercorn for production yet.

[pjirsa]

closing until opentelemetry is refactored to work with hypercorn