Better API for accessing coordinates on a Mesh

[trexfeathers]

✨ Feature Request

It should be easier to access the desired coordinate within a Mesh, taking into account that location and axis are commonly used filters, and that these are often dynamic.

Motivation

I'm always frustrated when I have to write code like this:

iris/lib/iris/experimental/ugrid/mesh.py

Lines 2736 to 2738 in 6adac1b

	# Location is either "edge" or "face" - get the relevant coord.
	kwargs = {f"include_{location}s": True, "axis": axis}
	location_coord = self.mesh.coord(**kwargs)