I03 DCM pitch lookup table should be improved to use discontinuous interpolation function

Whilst testing the PR for DiamondLightSource/hyperion#986 Neil explained to me that currently the lookup table in BeamLineEnergy_DCM_Pitch_converter.txt is not as good as it can be because GDA requires the lookup table to be a continuous function, whereas ideally it should be more like the undulator gap lookup table, i.e. have repeating x-coordinates at the discontinuities.

The LookupTableConverter implementation used for DCM pitch should be changed out for a new one that can support discontinuities to allow this.