Add featured downloads

[hugovk]

Description

• On download pages such as https://www.python.org/downloads/release/python-3140/, it's not immediately clear what to click in the big table of a dozen files.

• Let's add the most common ones as feature downloads at the top.

Closes #2419

Before

After

Notes

Each "Release" object in the CMS has a number of release files. Some of these have a "Download button" boolean set, max one per OS, which is used for displaying it at https://www.python.org/downloads/:

Let's also use this flag to decide what to feature here.

(Aside: the flag is set during the release process by download=True in https://github.com/python/release-tools/blob/d8077eae1dcea2653775e4b3ba9f51700b354f5e/add_to_pydotorg.py#L105-L190.)

Windows

However, for Windows, let's use the Python install manager and link to https://www.python.org/downloads/latest/pymanager/ using similar logic for the button at https://www.python.org/downloads/

That page says:

The install manager can install versions of Python as far back as 3.5, but only supports Windows 10 operating systems (or Windows Server 2022) and later.

Re: "The install manager can install versions of Python as far back as 3.5"

So let's only show the install manager for downloads of 3.5 and later. Older ones can use the file set by the CMS. For example, for 3.4.0:

Re: "but only supports Windows 10 operating systems (or Windows Server 2022) and later"

For the purpose of this featured release for 3.5+, it's fine to cater for the common case of new Windows (especially as Win10 is EOL). The full list is right there if you need a file.

@zooba How does this sound?