Rename some arguments called "position"

[KoBeWi]

When you connect Tree's empty_clicked argument to the same Tree or just any Control node, you will get a warning that the argument position of the newly generated callback shadows a property.
I went and renamed all arguments that could cause such warning.

Bugsquad edit: Closes godotengine/godot-proposals#5715

[Sauermann]

resolve godotengine/godot-proposals#5715

has a broader scope than #78864

[AThousandShips]

Wanting the dotnet team to take a look concerning renaming and compatibility, I forget the specifics on what constitutes breaking compatibility there (as this is a non-critical change)

[KoBeWi]

AFAIK _input_event might break compatibility, because C# supports named arguments. Signal changes only affect newly created callbacks.

[raulsntos]

Signal changes won't break compat in C#, lambda parameter names don't have to match.

Changes to method parameters will break source compat but only if the call-site is using named parameters, not sure how common that is but I find it unlikely here specially since AFAIK a virtual method like _input_event is only meant to be called by the engine and not users directly. Also, breaking source compat is not very disruptive anyway, so I think the changes here are fine.

[Sauermann]

Currently users get a "shadowing" warning for simply "doing the right thing". This should be fixed.

As mentioned above, compatibility is likely no problem.

While I would prefer event_position in CollisionObject3D to account for InputEventScreenDrag and InputEventScreenTouch, I guess mouse_position is also fine, because it covers the largest part of use-cases.

[Mickeon]

I'd rather go with event_position as the other input events are also supported, so for me naming it "mouse position" feels like dumbing its usefulness down too much. Any possible ambiguity needs to be clarified on the docs side.

[akien-mga]

Thanks!