Add support for Spot with arm

[wbthomason]

This PR adds support for the Boston Dynamics Spot robot, based on the URDF files available here: https://github.com/bdaiinstitute/spot_description.

It also includes some minor fixes to the random_dance.py script for compatibility with the latest VAMP.

There's one issue to resolve before merging: for some reason, at least on ARM (MacBook Air M2), Halton sampling appears to be buggy (not only for Spot) and only returns non-zero values for the first 4 degrees of freedom.
We should resolve this issue just in case it's somehow caused by this PR (though I doubt it - I more suspect a Mac issue or a regression due to the recent change in robot kinematics generation backend).

[wthomason-bdai]

@zkingston this does not appear to be a Mac-only issue; I can reproduce it on Ubuntu. Additionally, I'm seeing some sort of hang in validate...

More specifically: only for spot, I'm still seeing the RNG issue (on Linux) and validate seems to hang forever. On Mac, validate ran correctly.

[wbthomason]

I fixed the RNG issue (undefined behavior during access beyond bounds of a SIMD vector when converting to a float array), and the Spot can now plan! I also found that the observed hangs seem to come from an issue with RRTC going to a huge number of iterations - my running theory is that we're hitting the limits of the nearest neighbors structure, given the number of samples + the high dimensionality of the Spot relative to other supported robots, but I'm not sure about this. The need to take so many iterations (300k+) is likely due to the naive guesses I used for the Spot's validation fineness and RRTC range, or due to the SRDF used to generate the Spot's fkcc missing some important disallowed collisions. Still, I think this support is OK for now, maybe modulo @zkingston tuning of the RRTC range etc. I'll see if I can get a more refined SRDF.

[wbthomason]

As an aside, I'm not sure why the format check is failing? I've run clang-format on the relevant file, I think.

[wbthomason]

I've added support for a variant of the Spot with only its arm left free - this seems to work reliably (based on a bit of random_dance testing, nothing in-depth yet). I tried also tuning the RRT range down slightly, but no change for the full Spot.

[claytonwramsey]

all looks good to me!

you weren't lying about compilation times though:

Successfully installed vamp-planner-0.6

________________________________________________________
Executed in  141.42 secs    fish           external
   usr time  320.50 secs    0.00 micros  320.50 secs
   sys time   10.50 secs  396.00 micros   10.50 secs

[claytonwramsey]

may want to pick out these changes as a separate PR since that will be way easier to merge

[claytonwramsey]

should we remove panda_sphere_cage since this is a very similar experiment? Or leave it since it's the easiest example to reproduce?