*_map should be aware of category_orders and "leave room" for missing categories

[nicolaskruchten]

In the following examples, all markers of the same letter should have the same color, except in the last case, the a markers would have the specified color from color_discrete_map.

px.scatter(... color=["a", "c", "b", "d"], category_orders=dict(color=["a", "b", "c", "d"]))
px.scatter(... color=["a", "c", "a", "c"], category_orders=dict(color=["a", "b", "c", "d"]))
px.scatter(... color=["b", "d", "b", "d"], category_orders=dict(color=["a", "b", "c", "d"]))
px.scatter(... color=["a", "c", "b", "d"], category_orders=dict(color=["a", "b", "c", "d"]), 
    color_discrete_map=dict(a="red"))

This is technically a breaking change, so we'll release this in v5.