Fix CubicCurve::iter_samples iteration count

[jannik4]

Objective

Fix CubicCurve::iter_samples iteration count.

Solution

If I understand the function and the docs correctly, this should iterate over 0..=subdivisions instead of 0..subdivisions.
For example: Now the iteration returns 3 points at subdivisions = 2, as indicated in the documentation.

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[cart]

I'm not sure the docs are right here. The docs essentially say that "subdivisions" is the count of the number of "sections". However in my experience "subdivisions" is a count of the number of dividing lines. 1 subdivision = 2 sections, 2 subdivisions = 3 sections. Blender avoids this by using "number of cuts" terminology instead of "subdivisions". Godot calls this "subdivisions". We also call this "subdivisions" for the Plane shape.

Imo we should either:

1. Use different terminology for this curve functionality : sections, samples (although this is confusing because it is unclear whether the start and end are included), number of cuts, etc
2. Synchronize the "subdivision" behavior everywhere in the engine. I believe it should be "number of cuts".

[jannik4]

I agree that the terminology may be unclear and may need to be aligned with other parts from bevy.

However, I still think this PR has value in the short term regardless, since currently all methods like iter_positions do not include the endpoint, which is definitely wrong.

[cart]

Ok I buy that!