[Python APIView] optional dependencies in public API

[swathipil]

We want to make sure that we can load and parse libraries that use optional dependencies in the API. Currently, the parser fails because we haven't imported necessary dependencies.

Example: azure-quantum.

Best fix currently: Read and install dependencies from extras using the pkg_resources module before parsing.

[lmazuel]

Note that some extra can be OS requirements like

    extras_require={
        ':sys_platform == "win32"': [
            'windows-specific-package1',
            'windows-specific-package2',
        ],
    },

That means to install only on Windows. so we likely wouldn't want to install that blindly. I'm sure pkg_resources provides some form of helper to recognize who's is what (maybe the starting : is a sign, that we should ignore that key? Just thinking out loud)