MPPI: Support Low Accelerations, Asymmetric Accelerations, and increased acceleration smoothness

[SteveMacenski]

This provides proposed fixes to MPPI which allows for low acceleration profiles, asymmetric acceleration profiles, and much more smooth robot behavior with smoother acceleration and handling.

When using low accelerations, take care to reduce the STD of your robot's axes to reduce the chatter in that axis.

TODO

• Expose SGF order as a parameterization for simpler smoothing if users don't want to fine tune
• Test on Dexory or other platforms to ensure works OK on hardware
• Create a blog post of the write up perhaps? Or just put somewhere in the docs for future keeping
• Remove debugging acceleration logs and members
• Evaulate runtime computational impact from these changes
• Option to toggle on/off clamping velocities
• Create necessary docs.nav2.org of new parameters, tuning guidance for low-accelerations or other changes (STD tuning, SGF order 1 can oversmooth to help but will be more sluggish at the risk of not being able to make fine technical moves)

[tonynajjar]

FYI I merged main into your branch