Link Runner release documentation into the handbook

We should document the process of runner release so that anyone on the team can do it. Additionally we should document our policy for when we will release a patch version (what qualifies as "necessary and worth the effort") so everyone will have clear expectations about when bug fixes will arrive. And how to request it and select the right branches. Currently we just need to "know" who to ask (@ggeorgiev_gitlab).

Example, figuring this out over Slack: https://gitlab.slack.com/archives/C0199KBMY59/p1685705540807069