Nexus vdb import needs to handle LAB units

At present, the resqpy code for importing from Nexus runs assumes that the length units are metres or feet. For LAB units, it should be cm. Units of measure for the various array properties need to be set appropriately for LAB units as well.

Start by locating the resqpy code that imports from Nexus and trace how length units and array-property units are assigned. Compare the existing metres and feet handling with the required LAB behavior, where lengths use cm; done means LAB imports use the correct units throughout and existing unit handling remains intact.

Written by the indexing model from the issue text.