15 m/s is about 50 ft/s, which is way above what FRC robots should be
able to achieve. This limit lets us catch user errors from bad unit
conversions immediately instead of the LUT generation in the LTV
controllers hanging for a really long time.
Fixes#5027.
This adds a unicycle controller that's a drop-in replacement for Ramsete
and a differential drive controller that controls the full pose and
outputs voltages. The main benefit is LQR-like tuning knobs using a
system model.
