Add a curve sampling method to the AnimationClip API

[Hilpogar]

Objective

Add a method to AnimationClip to sample a property at a specific time. This is the first point proposed in #23355. The original goal was to allow the development of root motion, but it turns out that this API improvement can be useful for third party crates or games that need to sample animation curves directly. This PR is also inspired by the previous work in #16395.

Solution

Add a method sample_clamped to AnimationClip :

pub fn sample_clamped<P: AnimatableProperty>(
    &self,
    animatable_property: P,
    target: AnimationTargetId,
    time: f32,
) -> Option<P::Property> {}

This method requires to add another sample_clamped method to the AnimationCurve trait:

fn sample_clamped(&self, t: f32) -> Box<dyn Any>;

Testing

There is 2 new tests. One at the AnimationCurve level and one at the AnimationClip level. There is also an example in the method's documentation.

[alice-i-cecile]

@emberlightstudios I'd love your review here :)

[alice-i-cecile]

Surprisingly simple and well-motivated.

[emberlightstudios]

Sorry, I got side tracked with life stuff and had to shelve my project for some time. It looks good, but I see everyone already agreed on that.

[Hilpogar]

@emberlightstudios No problem, thank you for your original proposition it helped me a lot for the implementation ! This PR was for one of the intermediate steps but the final part is not merge yet. I would be happy to have your review if you have the time : #24201