Debug render spatial queries

[Jondolf]

Objective

It can often be useful to visualize spatial queries like raycasts and shapecasts.

Solution

Add debug rendering for RayCaster and ShapeCaster. SpatialQuery methods aren't debug rendered to avoid requiring mutable access to Gizmos in all of the methods, but PhysicsDebugRenderer now has utilities for rendering e.g. raycasts for those who need it.

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Todo

• Debug render raycasts
• Debug render shapecasts

Other changes

• Renamed "ray cast" and "shape cast" in docs to "raycast" and "shapecast"
• Fixed issue with multiple hits in shapecasts
• Fixed documentation for ShapeHitData