refactor: merge Rigidbody2D and Collider2D into PhysicsBody2D

[AnthonyWadham]

TL;DR

Consolidated Rigidbody2D and Collider2D components into a single PhysicsBody2D component that contains both rigid body parameters and collider shapes.

What changed?

• Removed the separate Collider2D component and moved its Shapes field into PhysicsBody2D
• Renamed Rigidbody2D to PhysicsBody2D and added the shapes array to it
• Updated NewPhysicsBody2D constructor to accept shapes as variadic parameters
• Modified all internal systems to work with the unified component structure
• Updated component queries to use PhysicsBody2D instead of separate Rigidbody2D and Collider2D components
• Renamed internal methods like applyRigidbodyInPlace to applyBodyParamsInPlace and RigidbodyDiffers to BodyParamsDiffer
• Updated shadow state tracking to use the consolidated component
• Changed validation and reconciliation logic to handle the unified structure

Why make this change?

This consolidation simplifies the physics component architecture by combining related data (rigid body properties and collision shapes) into a single component, reducing the complexity of managing separate but tightly coupled components and making the physics system more cohesive.

[AnthonyWadham]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat: physics2d Cardinal integration tests #881
• refactor: merge Rigidbody2D and Collider2D into PhysicsBody2D #886 👈 (View in Graphite)
• feat: add ShapeTypeStaticChainLoop and ShapeTypeEdge collider shapes #883
• feat: add Box2D physics2d plugin with CGO #880 : 1 other dependent PR (#882 )
• main

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