refactor snap_down support_surface setup for AO links

[aclegg3]

Motivation and Context

This PR refactors support_surface_id setup for ObjectSampler's use of snap_down function for Receptacles attached to articulated links. Previously, the code would allow snapping to the link or the body. Instead, only snapping to the link should be allowed.

How Has This Been Tested

CI

Types of changes

• [Development] A pull request that add new features to the habitat-lab task and environment codebase. Development Pull Requests must be small (less that 500 lines of code change), have unit testing, very extensive documentation and examples. These are typically new tasks, environments, sensors, etc... The review process for these Pull Request is longer because these changes will be maintained by our core team of developers, so make sure your changes are easy to understand!

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)
• [ ] I have added tests to cover my changes if required.