Character controller improvements

[AMZN-Liv]

Is your feature related to a problem? Please describe
There are existing issues with collision and hit detection with EMFX and Ragdolls that make it more challenging to develop character controllers. The existing implementation wraps around PxController and is missing utility functions and callbacks that would be helpful to expose. Additionally, there are some reported performance issues and unexpected default behavior where the controller is not affected by gravity out of the box.

Describe the solution you'd like
We should deep dive into the short, medium, and long-term improvements that have been identified to address these pain points. Longer-term, this may include work to migrate the character controller update to AZ::Event, expose the callbacks to edit and behavior contexts and controller-controller interactions, expose collision state of the character controller to Script Canvas, and more.