Example: 3d particles on a 2d plane

[joaander]

Description

Add a new example that demonstrates 3D interaction models (in this case, hard capsules) where the body centers are confined to a 2D plane.

To achieve this example, I needed to relax many Microstate trait bounds so that B and P could hold positions in different vector spaces.

I also added 3D orbit camera controls to hoomd-bevy.

Motivation and context

Give users a starting point for quasi-2D simulations.

Resolves #234
Resolves #331

How has this been tested?

I ran the new example locally, and it behaved as expected. The GSD output renders as expected in OVITO, which has native support to render capsules.

Checklist:

• I have reviewed the Contributor Guidelines.
• I agree with the terms of the hoomd-rs Contributor Agreement.
• My name is on the list of contributors (doc/src/credits.md) in the pull request source branch.
• I have summarized these changes in release-notes.md following the established format.