LArPhysWavePredictor: Use supercell identifier-helper if needed, use unique_ptr, santize loop
While working on something else, I discovered that the LArPhysWavePredictor was using the regular offline helper even if working on SuperCells. This qualifies as bug, though I am not sure if the code-paths where the offline identifier helper is used are executed when processing SuperCell calibration runs.
This MR fixes the supercell-identifier-helper issues on top of some technical improvments like using unique_ptr instead of bare poiner.