Drop duplicate or almost-duplicate edges

[tomalrussell]

Test for almost-equal lines, and/or equal geometries with different coordinate lists.

shapely has equals and almost_equals: https://shapely.readthedocs.io/en/stable/manual.html#object.equals

Consider buffer/contains test:

def almost_equals(a, b, tolerance):
    return a.buffer(tolerance).contains(b) && b.buffer(tolerance).contains(a)

Related concepts around smallest max distance between shapes - Hausdorff distance, Fréchet distance