Mark pip index versions as not experimental

[KrishanBhasin]

The second part of #13188, after #13194.

[notatallshaw]

I see no issue with this PR, so if no one raises any concerns in the next few days I will merge.

[ichard26]

I do want to take a look at this PR. I'll get this reviewed in a few days.

[pfmoore]

@notatallshaw just a gentle ping - it's been 3 weeks since you said you were going to merge this. It would be nice to get it off the list of things still to do for 25.1.

[notatallshaw]

@ichard26 do you still want to review further? Otherwise I'll merge this week.

[notatallshaw]

With no further comment I am merging, it functionaly works:

$ pip index versions requests
requests (2.32.3)
Available versions: 2.32.3, 2.32.2, 2.31.0, 2.30.0, 2.29.0, 2.28.2, 2.28.1, 2.28.0, 2.27.1, 2.27.0, 2.26.0, 2.25.1, 2.25.0, 2.24.0, 2.23.0, 2.22.0, 2.21.0, 2.20.1, 2.20.0, 2.19.1, 2.19.0, 2.18.4, 2.18.3, 2.18.2, 2.18.1, 2.18.0, 2.17.3, 2.17.2, 2.17.1, 2.17.0, 2.16.5, 2.16.4, 2.16.3, 2.16.2, 2.16.1, 2.16.0, 2.15.1, 2.14.2, 2.14.1, 2.14.0, 2.13.0, 2.12.5, 2.12.4, 2.12.3, 2.12.2, 2.12.1, 2.12.0, 2.11.1, 2.11.0, 2.10.0, 2.9.2, 2.9.1, 2.9.0, 2.8.1, 2.8.0, 2.7.0, 2.6.2, 2.6.1, 2.6.0, 2.5.3, 2.5.2, 2.5.1, 2.5.0, 2.4.3, 2.4.2, 2.4.1, 2.4.0, 2.3.0, 2.2.1, 2.2.0, 2.1.0, 2.0.1, 2.0.0, 1.2.3, 1.2.2, 1.2.1, 1.2.0, 1.1.0, 1.0.4, 1.0.3, 1.0.2, 1.0.1, 1.0.0, 0.14.2, 0.14.1, 0.14.0, 0.13.9, 0.13.8, 0.13.7, 0.13.6, 0.13.5, 0.13.4, 0.13.3, 0.13.2, 0.13.1, 0.13.0, 0.12.1, 0.12.0, 0.11.2, 0.11.1, 0.10.8, 0.10.7, 0.10.6, 0.10.4, 0.10.3, 0.10.2, 0.10.1, 0.10.0, 0.9.3, 0.9.2, 0.9.1, 0.9.0, 0.8.9, 0.8.8, 0.8.7, 0.8.6, 0.8.5, 0.8.4, 0.8.3, 0.8.2, 0.8.1, 0.8.0, 0.7.6, 0.7.5, 0.7.4, 0.7.3, 0.7.2, 0.7.1, 0.7.0, 0.6.6, 0.6.5, 0.6.4, 0.6.3, 0.6.2, 0.6.1, 0.6.0, 0.5.1, 0.5.0, 0.4.1, 0.4.0, 0.3.4, 0.3.3, 0.3.2, 0.3.1, 0.3.0, 0.2.4, 0.2.3, 0.2.2, 0.2.1, 0.2.0

If there are missing docs or features they can be added in follow up PRs.