Add a 'random' video sort option

[ppom0]

Describe the problem to be solved

I operate a small instance of curated videos that can be looked in any order.

To improve video discovery, I want videos to be presented randomly at users.

Describe the solution you would like

I first wrote a hacky plugin (see #6759) that completely overriden the core logic of video listing to do it.

I just updated to 7.x, where the patch didn't work anymore, as the video listing presentation has changed.

So I wrote a patch directly in Peertube here: https://github.com/Chocobozzz/PeerTube/compare/develop...ppom0:PeerTube:random

The random seed is based on the current day, so that randomness changes every day.

The patch already works on my instance.

If you're interested, I can rebase on develop, remove random as a default sort option and discuss immplementation on a pull request.