• Added support for Python 3.15 and support for C extensions generated by CFFI
  to target the new abi3t free-threaded ABI.
• Dropped support for Python 3.9.
• Added cffi-gen-src CLI to generate CFFI C extension source for alternate build backend support.
• Fixed crashes inside __delitem__.
• Fixed "string too big" error under MSVC.
• Fixed mingw builds.
• Added support for arm64 iOS wheels.