Use smooth duty universally

[lukash]

Duty cycle can spike a lot, the purposes it's used for can all benefit from the mild smoothing we already have. Unify the usage and only use smooth duty for everything.

@surfdado putting this into a PR so that you have a chance to comment, WDYT? The motivation is smoother duty for the haptic duty alert (I had some spikes trigger it during normal riding). Please add a review if you don't mind.

Untested at the time of posting the PR, I'll only merge after I test it, but it's basically just the duty pushback and the wheelslip detection that uses the duty value.