DEV: patchbot: add the AI-based bot to pre-select candidate patches to backport

DEV: patchbot: add the AI-based bot to pre-select candidate patches to backport

This is a set of scripts, prompts and howtos to have an LLM read commit
messages and determine with great accuracy whether the patch's author
intended for the patch to be backported ASAP, backported after some time,
not backported, or unknown state. It provides all this in an interactive
interface making it easy to adjust choices and proceed with what was
selected. This has been improving over the last 9 months, as helped to
spot patches for a handful of backport sessions, and was only limited by
usability issues (UI). Now that these issues are solved, let's commit the
tool in its current working state. It currently runs every hour in a
crontab for me and started to prove useful since the last update, so it
should be considered in a usable state now, especially since this latest
update reaches close to 100% accuracy compared to a human choice, so it
saves precious development time and may allow stable releases to be
emitted more regularly.

There's detailed readme, please read it before complaining about the
ugliness of the UI :-)