Fix multiple issues with test_body_motion() and test_body_ray_separat…

…on().

The test_body_motion() and test_body_ray_separation() functions perform an
initial recovery step to attempt to move the body to a safe place before
testing whether the body can safely move. Currently this is done in four
partial steps, and during each step the detected penetrations are reversed
by summing them together.

This patch changes this approach to a single step and uses the maximum
penetration instead of the sum. The same approach is applied to Godot
Physics 2D, 3D and Bullet Physics, and to both CollisionShapes and
RayShapes.

Also, fixes Bullet physics not detecting collisions and relying on the
recovery step. Furthermore, ensures that Bullet physics only moves a
safe amount by using a binary search as done in Godot physics.