Modularize 'cqlsh' for use in python imports and better support for Windows installations

[bschoening]

This patch is designed to better integrate this PyPI packager with Apache cqlsh. It does not make code changes to cqlsh.py.

The changes here create a new module 'cqlsh', which is required to use setuptools' Entry Point (https://setuptools.pypa.io/en/latest/userguide/entry_point.html). Entry points provide better platform installation; on Linux it will create a shell script for 'cqlsh' which calls the module; on Windows it will create an .exe file. Currently, this package isn't easy to run on Windows because a file without an extension is not executable.

Note: I've tested these changes on both Linux (MacOS) and Windows 11. The test version of the package can be found at https://test.pypi.org/project/cqlsht/ and installed with:

On Linux, the executable cqlsh file created by setuptools looks like this:

$cat /usr/local/bin/cqlsh
#!/usr/local/opt/python@3.9/bin/python3.9
# -*- coding: utf-8 -*-
import re
import sys
from cqlsh.__main__ import main
if __name__ == '__main__':
    sys.argv[0] = re.sub(r'(-script\.pyw|\.exe)?$', '', sys.argv[0])
    sys.exit(main())

[jeffwidman]

Thanks for the hard work here!

1. Can you break out the deprecated dep as a separate PR? It's different scope then the other changes here and as noted in https://github.com/jeffwidman/cqlsh/issues/4#issuecomment-1008186919 there's a little more research needed before we can merge that. My experience in open source is keeping the scope of individual PR's smaller makes them easier to discuss/merge w/less risk.
2. I think it's a great idea to make this easily importable and use entry_points... def interested in merging that functionality.

[bschoening]

Reverted the deprecated dependency change #4

[jeffwidman]

Thank you!