GDNative: merge API structs, bump version of merged structs.

[bruvzg]

Merge all core API functions from the old incompatible structs to the new single "Core API 2.0" and extension API functions with multiple sub-versions to the new single structs, bump version of the new structs, as was suggested in #39064.

[akien-mga]

CC @godotengine/gdnative

[touilleMan]

LGTM 👍

[BastiaanOlij]

I'm a fan of this, my only remark is that I would sync the major version number up with Godot, so instead of setting it to 2, set it to 4.

[bruvzg]

so instead of setting it to 2, set it to 4.

Changed it to 4.

[akien-mga]

Thanks!

[Anutrix]

This seems like a big update to GDNative. More explanation regarding this would be nice. Something like an article on the main site or on a periodically updated Release/Dev Notes page on docs site.

[akien-mga]

This is pre-alpha, compatibility breaking changes to make things match the pre-alpha, compatibility broken master branch. Not really news worthy. There will be articles when there are things to talk about for sure, and that will involve the merge of the GDNative API structs, but for now it's not very useful to know about it when it's a year away from being released and usable.