Trim docker image size

[3nprob]

• docker: Remove redundant pip install wheel
  • Since the bookworm upgrade (build(docker): update to debian bookworm #1771), the image already comes with python3-wheel 0.38
• install.sh: Only install/upgrade setuptools and pip in venvs
  • I think we can assume people have recent enough versions at this point? And if not seems better to have users solve it themselves and/or steer them to using venv, rather than having the joinmarket install script potentially clobber the system-wide
• docker: remove build-time debian package dependencies from final image

Significantly reduces image build time.
Reduces final image size by 43%.