Introduce 3.14 and drop 3.9 Python image generation

Python pre-releases

• Use rc tag, unstable Python version
• Try to build image
• Introduce with build dependencies installed in the meantime
  • gcc required to build msgpack and other dependencies required otherwise assert.h is missing
  • Alpine: build-base or alpine-sdk
  • Debian: gcc and libffi-dev
• Try to build Silkaj and DuniterPy

Python stable release

• Remove build-base once no longer necessary, once Py3.14 wheels are provided to run poetry install
  • Once msgpack provides Py3.14 wheels
• Remove rc tag once Python 3.14 is released as stable
• Drop Python 3.9 image generation

Post

• Create follow-up ticket for Py 3.15/3.10: Introduce 3.15 and drop 3.10 Python image gener... (#13)