Make pywin32_postinstall and pywin32_testall into Console Scripts

[Avasam]

Probably a good idea to get postinstall tests first: #2392

Closes #1855 by obsoleting it. It integrates the same idea of moving the script into a pywin32 package so it can be run as a module (python -m win32.scripts.pywin32_postinstall -install), but with far less changes.
It also registers it as a console script, which means users can simply call pywin32_postinstall -install.

The same was done for pywin32_testall since it was also already shipped as a Script.

I've been doing some reading and if this works, it should be a really clean solution.
Doc: https://setuptools.pypa.io/en/latest/userguide/entry_point.html#console-scripts
Results:

[Avasam]

I'm keeping this for now as to not break some poor sysadmin's workflow of looking in Python's Scripts folder 😉 (then again, they were probably using .exe installers, but it's barely 4 lines to keep the support)

[mhammond]

I don't understand how the commit message relates to this PR, nor how the post_install script is run automatically?

[Avasam]

nor how the postinstall script is run automatically?

It doesn't (and can't when shipped as a wheel due to the current wheel specifications). This is simply an easier way for users to run the postinstall script without having to know or navigate to their Python install's scripts or lib folder.

It integrates the same idea as #1855 of moving the script into a pywin32 package so it can be run as a module (python -m win32.scripts.pywin32_postinstall -install), but with far less changes.
It also registers it as a console script, which means users can simply call pywin32_postinstall -install.

The same was done for pywin32_testall since it was also already shipped as a Script.

(I've updated the PR description with this explanation)

[Avasam]

Suggested change

	run: python -m win32.scripts.pywin32_testall -v -skip-adodbapi
	run: python win32/scripts/pywin32_testall.py -v -skip-adodbapi

The failing test https://github.com/mhammond/pywin32/actions/runs/12308761196/job/34354669586?pr=2408#step:7:316 and comment

# Run the tests directly from the source dir so support files (eg, .wav files etc)
# can be found - they aren't installed into the Python tree.

tell me that it maybe didn't even make sense that the test was shipped in the first place (or could be modified to skip some tests when not run from source)

[Avasam]

I fixed the location reference in pywin32_testall.py and now it's all passing ! I'll try to get #2392 working as well for safety.