Migrating issues to discussions

[Xrayez]

So, we've recently enabled GitHub's Discussions feature for this repository, and I wonder whether it's worth to just migrate all Issues to Discussions now (it's fairly easy to do).

I'm not quite sure if there's much benefit in assigning labels to issues all the time, and oftentimes what can be implemented in core can also be implemented in a module 95% of the time, and what can be implemented in a module can be implemented in a plugin 70% of the time. Instead, people can just choose in which category they'd like to create a new discussion in themselves currently. Discussions can be further categorized, if needed.

Discussions are oftentimes open-ended, and there should be no notion of discussions being "open" or "closed", because this only creates a false premise that ideas can be approved or rejected. Nobody is forced to do anything.

Discussions can also happen in a tree-structure (you can reply to each post).

Some of the GitHub's Discussions features are showcased in godotengine/godot-proposals#2069 as well.

[Xrayez]

I have converted issues to discussions now (except trackers, because they are supposed to be cross-referenced with other issues with Godot, apparently discussions don't support cross-referencing).