Fix SkeletonModification2DLookAt with negative scales

[thiagola92]

Fixes #80252.

This is an attempt to fix SkeletonModification2DLookAt when only one scale is negative.

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Instead of getting the transform and operate over it, changes will happen through Node2D methods. I'm doing this because we can't decompose X negative scale from transforms, which means that you would have to replicate what Node2D already does (recovering the correct scale).

I'm operating over the angle and only at the end call methods like set_rotation() (i'm just reducing method calls).

Adding X to local rotation would also means that the global will increase by X, right? That's why I'm just adding to global rotation without any conversion.

[YuriSizov]

You have two PRs, this and #81051, that refer to the same two issues. Are they both required to fix both of the issues, or how does this work?

[thiagola92]

You have two PRs, this and #81051, that refer to the same two issues. Are they both required to fix both of the issues, or how does this work?

Sorry, saying that fixes #75224 is wrong! The issue is saying that all IK modifications fail scaling X negatively and I'm just fixing for two modifications (SkeletonModification2DLookAt SkeletonModification2DTwoBoneIK).

Having said that... I'm still unsure about the solution, after reading @lyuma old proposal I started questioning if It could be solved other way.

[thiagola92]

@YuriSizov I started a personal project to better understand the subject and I believe that this part is correct.