Prelim Sys Id Prototype Stuff

This is just a code snapshot from Anzu, some stuff not yet exported. Consider this "for demonstration purposes" / "in the noise" until it's proven effective on hardware (or discarded otherwise).

Still needs code review, etc. etc.

Setup

Only tested on Ubuntu 22.04, CUDA 11.8 (though GPU isn't strictly necessary).

Should install prereqs for Drake: https://drake.mit.edu s

Build and Test

cd drake_sys_id
bazel test //...

Will take a while because Python bindings have to build.

WARNING: For some reason, //sys_id:drake_torch_sys_id_test seems to run 5-10x slower than it does in internal Anzu repository. Unclear why.