Replace pfsFiberTrace with pfsFiberProfiles

pfsFiberTrace contains both the profile and the position of the trace, but the position of the trace is also in the detectorMap, a confusing duplication. Furthermore, because the pfsFiberTrace contains the profile realised for a particular trace position, it's not possible to realise the profile at a different position (the profile is undersampled, so we can't just resample). In order to be able to realise the trace at a different position, we need to store the profile, and not the realised profile.

I propose to replace pfsFiberTrace in the datamodel with a new object, pfsFiberProfiles.