Add ONE constants to Vector2 and Vector3

[KellyThomas]

also updates class documentation xml
fixes #22806

[samgreen]

Haha, well done. You beat me by moments.

[ghost]

I think it would also be a good idea to add them to Mono, like you did with the original constants in #20901.

[akien-mga]

zero

ONE

If that isn't obfuscation 🤔

[KellyThomas]

@Homer666
The mono vectors have had One for a while:

https://github.com/godotengine/godot/blob/master/modules/mono/glue/Managed/Files/Vector3.cs#L294

https://github.com/godotengine/godot/blob/master/modules/mono/glue/Managed/Files/Vector2.cs#L253

[KellyThomas]

@akien-mga
Thanks, the commit message has been fixed too.

[aaronfranke]

This PR is missing the documentation changes. https://github.com/godotengine/godot/blob/master/doc/classes/Vector2.xml Note that the doc for zero vectors is wrong (for some reason it's called "Null vector" instead of "Zero vector") so you could fix that up too while you're at it.

[KellyThomas]

@aaronfranke Good idea! The documentation has been added.

[akien-mga]

Thanks!