YANG Tools Fluorine Release Plan

Fluorine development cycle of yangtools will focus on hardening existing codebase, be it bugfixes or performance improvements. For this we will retain the 2.0.x branch, which follows strict ABI compatibility rules, so that it is consumable by both Oxygen and Fluorine release trains.

As a stretch goal, we will attempt to define building blocks required to solve YANGTOOLS-418, so downstreams (most notably MDSAL and Controller) can start preparing to receive the 3.0.0 release, which will include it.