BlackSheep Files

• Add support for PyPy, adding a pure-Python fallback for all Cython modules.
• Fix #539. Make httptools an optional dependency, to support PyPy.
• Modify url.pyx to remove the dependency on httptools.
• Modify the HTTP Client implementation in BlackSheep to not be tightly coupled with httptools for the response parsing logic, and include built-in support for h11.
• MINOR BREAKING CHANGE. Since httptools is not installed by default, the BlackSheep client requires either httptools or h11 to be installed, as it does not implement its own parsing logic for HTTP responses. This affects only the HTTP client.
• Upgrade dependencies (see pyproject.toml for more information).
• Include a pure-Python wheel in the distribution package, and run tests with PyPy 3.11.
• Fix #559, which is a performance regression introduced in 2.3.0. Remove support for Pydantic v1 validate_arguments decorator (added in 2.3.0), which caused the regression. Pydantic's v2 validate_call supports async and does not require specific code.

Special thanks to @bymoye for helping with #539.