Running `setup.py` as a script and its use as a CLI tool are deprecated

[Avasam]

https://packaging.python.org/en/latest/discussions/setup-py-deprecated/#is-setup-py-deprecated

python setup.py and the use of setup.py as a command line tool are deprecated

https://setuptools.pypa.io/en/latest/deprecated/commands.html#running-setuptools-commands

running python setup.py directly as a script is considered deprecated.

pywin32 itself should move away from it, I have yet to investigate everything needed for pywin32 to move away from it.

Relates to #2119

To stop using python setup.py, the --skip-verstamp flag needs to be changed. Either trying to pass it through:

• --config-settings and --build-option / --global-option
• Environment variables
• Change version stamping to not have a bootstrapping issue in the first place, rendering this flag obsolete.
• or another mechanism I'm not aware of

Being able to build / install from pip install will open the door to:

• Building / installing the latest in-development version directly from a GitHub branch https://github.com/mhammond/pywin32/issues/2306
• editable installs, which itself:
  • Allows developer to test/import modules directly from the repo https://setuptools.pypa.io/en/latest/userguide/development_mode.html
  • Helps static checkers be more aware of which files should be present, during development. https://github.com/mhammond/pywin32/blob/9ef506138adc28b848cc537a9dc64cd18d2fcabd/pyrightconfig.json#L45-L51