[packaging] Explore compiling `libssh` statically

[webknjaz]

This would need to only concern wheels published to PyPI (manylinux et al.)
The downstreams should still retain the ability to link against the OS-provided libs.

Some research suggests that this is implementable though extra_objects and -fPIC:

• https://cython-users.narkive.com/ocKNbCAj/wrap-c-static-library
• https://groups.google.com/g/cython-users/c/gQQ1JUtckBE/m/hGb78MrNEGYJ
• https://github.com/cython/cython/blob/404d958/Cython/Distutils/extension.py#L21
• https://github.com/cython/cython/blob/404d958/Cython/Debugger/Tests/TestLibCython.py#L138
• https://github.com/cython/cython/blob/404d958/Cython/Build/Dependencies.py#L151
• https://stackoverflow.com/a/2106051
• https://setuptools.pypa.io/en/latest/deprecated/distutils/setupscript.html#other-options
• https://setuptools.pypa.io/en/latest/userguide/ext_modules.html#extension-api-reference