Finish robocasa example

[RussTedrake]

I've got a good start in book/mobile/robocasa.ipynb, but need to work on the texture support, etc.

Related to RobotLocomotion/drake#21958

[RussTedrake]

I'm going to pause this waiting on https://github.com/RobotLocomotion/group-miscellaneous/issues/24 .

[RussTedrake]

#425