Replace JBox2D with native implementation / JNI wrappers for some applicable targets

Hello! It would be nice to rely on a first-party Box2D implementation in korge.
That would allow keeping up-to-speed with Box2D updates (without relying on an outdated complete Box2D Kotlin/Java rewrite) and resolving JBox2D compute/memory performance considerations.

References:
https://stackoverflow.com/questions/31954012/whats-the-difference-between-jbox2d-and-libgdx-box2d
https://github.com/libgdx/gdx-box2d
https://box2d.org/posts/2023/01/starting-box2d-3.0/
https://gilspot.net/blog/m2z0uhrb5t9vgymuo8z14lrjfwyx6z

No files, tests, or entry points are named. Start by locating the current JBox2D integration in the repository and review the Box2D and libgdx-box2d references, then determine which targets are applicable. Done would mean a first-party Box2D implementation or JNI wrappers replace the relevant JBox2D usage while keeping the applicable targets working.

Written by the indexing model from the issue text.