Update the Python docs

[encukou]

Here's a big update to Python sections to keep them current.
The content was already reviewed by Python SIG members Zbyszek and Miro in encukou#1

---

Update the list of Python versions.
Remove sections for recently removed interpreters.

Change the section order to put Multiple Pythons near the top,
since this is one of the main selling points of Fedora wrt. Python.

Warn that pip installs third-party software.

Explain more clearly why virtual environments are preferred over
Fedora packages for development.

Only keep the name "virtualenv" for environments created by the actual
virtualenv tool; otherwise switch "virtual environment" or just "environment".

Update Flask docs to reflect best practice there.
Add ESP32 to the MicroPython docs.

And further rewordings and reorganization.

[pvalena]

Thanks for your PR, it looks great!

I've had some styling comments, but apart from that it LGTM.
Let me know if you want to keep it as it is - I'll leave it up to you.

[encukou]

I split the text out of habit (shorter lines make the source easier to read, at least to me). Since it doesn't affect the output, I'll keep the PR as it is.
If you have a stronger opinion, feel free to reflow the text.

[encukou]

Can this be merged?

[pvalena]

Sure, LGTM.

Note that at this point, unfortunately, there's no way of generating the actual website (any help is welcome).

[pvalena]

On the second thought- have you reviewed the result, does it actually build for you? (I'd be much happier to merge this if I could actually see it rendered correctly.)

[encukou]

No, I couldn't get the actual website to work locally. I rendered the markdown files using a different tool.

[pvalena]

Ok, thanks for the message. That's good enough for me- I'll merge it then, and get back to you with if there are some visible issues.