Add simulator physics collision cache.

[0mdc]

Motivation and Context

This adds a cache for the habitat-sim get_physics_contact_points() function.

This function is called multiple times a frame and is quite expensive.

On a reference single-learn HITL application, this improves the framerate from 11.3 to 13.8 FPS.

How Has This Been Tested

Tested locally + unit tests.

Types of changes

• [Optimization]

Checklist

• [x] My code follows the code style of this project.
• [x] I have updated the documentation if required.
• [x] I have read the CONTRIBUTING document.
• [x] I have completed my CLA (see CONTRIBUTING)
• [x] I have added tests to cover my changes if required.