Add position to set external forces and torques

[AntoineRichard]

Description

This PR adds the option to set wrench positions to set_external_force_and_torque. This is a non-breaking change as the positions are passed as an optional argument. When no positions are set, the function defaults to the original implementation, that is, no positions are passed to PhysX. The PR also adds tests to check that the position values are correctly set into their buffer, but does not check if the resulting wrenches are correct. I did test the Quadcopter task before and after this PR and the training results are exactly the same.

As of now, the function follows the original layout. But it could make sense to offer the option to set the position in either the link frame or the CoM frame. This would follow the recent changes made to the set_pose and set_velocity methods for instance. However, this would be a breaking change. Hence, for now, this has not been implemented. One could also argue, that this could be done prior to feeding the positions outside this method. Please let me know what you feel is best, and I'll update the PR accordingly.

If one wanted to test the resulting wrenches, it would require a simple test articulation like a 1kg sphere that would be used to accurately compute the expected velocities. This is also feasible, but I feel like this test is more on the PhysX side of things, let me know.

This change will require an update of the API documentation to include the position argument.

Fixes #1678

Type of change

• New feature (non-breaking change which adds functionality)
• 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

[kellyguo11]

Thanks for adding in the wrench positions. I think your current implementation is good for now. We are trying to address the com/link frame issue from the physics side so that we can avoid the additional transformations on our end.

[jtigue-bdai]

FYI update to the latest main you will find that we have reverted the "root_link" vs "root_com" deprecation. Please use the previous "root_" API.