--Add Panoptic/Instance ID support to Semantic sensor

[jturner65]

Motivation and Context

This PR will add the ability to have the semantic sensor produce images containing object ID of the objects rendered per-pixel in the same way that it currently produces semantic ID observations.

Until this PR in habitat-lab is merged, this PR will fail on lab tests due to hard-coded references to the stage ID.

NOTE (side thesis): This PR also refactors many uses of Eigen vec classes to Magnum instead.

How Has This Been Tested

Locally c++ and python tests pass

Types of changes

• [ ] Docs change / refactoring / dependency upgrade
• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have completed my CLA (see CONTRIBUTING)
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.