Adds stereolabs cameras and restructures `lab_assets` into robots and sensors

[pascal-roth]

Description

Add configurations for stereolabs cameras. In addition, restructures the lab_assets to be more structured by introducing a subdirectory with all the robot configs and one for the sensors.

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist

• [ ] I have run the pre-commit checks with ./isaaclab.sh --format
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• [ ] I have added my name to the CONTRIBUTORS.md or my name already exists there