Add SkeletonIK3D get/set_interpolation compat from #87888

[lyuma]

Adds both SkeletonIK3D functions mentioned in issue #90303

interpolation was moved to influence, so the compat methods forward to the influence getter/setter.

[dsnopek]

This should also remove these lines from 4.2-stable.expected:

Validate extension JSON: API was removed: classes/SkeletonIK3D/methods/get_interpolation
Validate extension JSON: API was removed: classes/SkeletonIK3D/methods/set_interpolation

We shouldn't need to ignore those messages with the new compatibility methods

[akien-mga]

Aside from David's comment, looks good to me.

[lyuma]

I tried removing the two lines as @dsnopek asked, but now it's complaining that the APIs I am adding i this PR were removing.

Any extension API experts out there able to figure out what I did wrong?

[akien-mga]

Those methods (and the property) actually need to be readded as normal methods, not as compat methods. Compat methods are for when we break compat by changing a method prototype.

Here, the old method bindings should just be brought back, but the implementation of these methods now defers to the new influence method.

Remember to also add the property back, and remove its line from the .expected file. And then in the doc XML, you can mark the property as deprecated.

All relevant code should be enclosed in #ifndef DISABLE_DEPRECATED.

[akien-mga]

Looks great now, should pass checks.

[lyuma]

I used PROPERTY_USAGE_NONE for the deprecated property, so it hopefully won't show in the inspector or get saved. Is that correct?

[akien-mga]

Yeah that sounds good to me.

[akien-mga]

Thanks!