Revert #57392 & rename Camera zoom to zoom_scale

[Mickeon]

Closes godotengine/godot-proposals#5525 (See proposal for further reasoning).

#57392 modified the Camera2D's zoom to behave more consistently and intuitively with real-life. Starting from Vector(1, 1), Higher values zoom in, and lower values zoom out.
It first seemed like a smart move. However, in actual practice, this results in the property being very difficult to work with.
The higher precision of zooming in is essentially not that useful, and zooming out is pretty restrictive.

This PR reverts the change to be like 3.x, and also renames the Camera2D's zoom to zoom_scale as it is already called in the internal code.

Do note that this property cannot be added to the Project Converter because it would conflict with GraphEdit's zoom, which in truth, also suffers from the same issue. It probably should be there changed, as well.

[Zireael07]

Do we have other reports that this makes the functionality more difficult to work with?

[Mickeon]

Doesn't have to be anything urgent, so let's give it time. This PR exists just to address it swiftly if there ends up being demand for it. Most casual users probably don't even realise this has been changed during the transition.

[ettiSurreal]

Doesn't have to be anything urgent, so let's give it time. This PR exists just to address it swiftly if there ends up being demand for it. Most casual users probably don't even realise this has been changed during the transition.

I agree, for now let's just wait and see if others have issues with it aswell.
If it does go through, we could maybe even support zoom_scale of zero, as in rendering only a single row of pixels.

[ettiSurreal]

Since some users seem to prefer the 4.0 behavior, i tried making a solution that hopefully gets the best of both worlds :)
godotengine/godot-proposals#5532

[akien-mga]

There's no consensus on this PR nor the proposal, so we won't do this change for 4.0.