Require gunicorn_h1c >= 0.4.1 for fast parser mode. Add new exception
types and limit parameters to PythonProtocol for parity with C parser.
Update tests to parametrize across both parser implementations.
Add test suite that exercises both PythonProtocol and H1CProtocol
implementations with identical test cases using pytest parametrization.
Tests cover request line parsing, headers, body handling (Content-Length
and chunked), connection handling, parser reset, and callback behavior.