Python: Limited C API support

[igo95862]

Python documentation describing the limited API: https://docs.python.org/3/c-api/stable.html#stable-application-binary-interface

Basically this will allow the Python C extension to be forward compatible. This requires the Py_LIMITED_API macro to be set and the extension have the .abi3.so suffix.

I tried using the name_suffix but it is disabled for extension_module.

sd_bus_internals_module = python.extension_module(
    'sd_bus_internals',
    sd_bus_internals_sources,
    dependencies : libsystemd_dep,
    c_args : ['-DPy_LIMITED_API=0x03070000'],
    install : true,
    subdir : 'sdbus',
    name_suffix : 'abi3'
)

Maybe it is worth support it in python module? For example, a new option limited_api : '3.7' would set the limited api to python 3.7 and put the abi3.so suffix.

[igo95862]

I found a merge request that implements this: #11745

[eli-schwartz]

Also #12008

[tristan957]

Closing as duplicate