A lot of the line measure traits were re-worked.

Mostly this is just moving code around in hopes of similar methods
across metric spaces being easier to find now that they are uniform.

It also enabled replacing some mostly copy/pasted implementations in geo
with generic implementations, which enabled some new functionality -
e.g. we can now `.densify::<Geodesic>`

One notable behavioral change: the output of the new `Bearing` trait is
now uniformly 0...360.  Previously GeodesicBearing and HaversineBearing
returned -180..180 while RhumbBearing returned 0...360.

georust/geo#1210

This actually uncovered a bug in ferrostar, reflected in the new output
of
ferrostar/src/snapshots/ferrostar__simulation__tests__state_from_polyline.snap

Since previously we were casting a potentially negative number to u16 —
now it's always positive (0...360).