Get velocities, efforts and wrench from Genesis Sim

### Description

While writing down the new API in #123, somehow we need to obtain vel, eff and wrench from a Genesis scene.

### References

_No response_

Start by reading the new API work referenced in issue #123 and determine how a Genesis scene exposes velocity, effort, and wrench data. Clarify the required return shape and scene entry point before proceeding; done means the API can obtain all three values from a Genesis scene.

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