deprecate exe installers

[mhammond]

As noted in #1936 (comment), .exe installers are deprecated almost everywhere else, and deleted from recent setuptools. Our CI no longer creates them to avoid pinning to old versions. The build environments necessary to create .exe installers are therefore stranded.

So we should formally deprecate our installers - something like:

• document it in README, invite discussion here.
• have the installers note it in the next release, pointing here.
• make whatever changes we can identify to smooth things for such users.
• stop producing them.

[Avasam]

@mhammond Other than "invite discussion here." and "pointing here.", it seems that the first 2 points are complete.

For point 3, is there anything that the installers still do that PyPI wheels don't?

For point 4, https://mhammond.github.io/pywin32_installers.html says:

you can't make them with recent versions. So at some point in the future they can't be provided.

Which leads to believe they could be dropped with Python 3.9 support (so some time after September 2025), since pywin32 is currently using Python 3.9 to build 3.10+ installers. Does that sound correct or do you have any plans of dropping them sooner?

[mhammond]

I have no plans here at all - these .exe artifacts have been downloaded many thousand times for the latest release, so I'll keep them alive as long as practical, but at some point I'll give up.