LArG4Barrel: const fixes for AccMap, PsMap and LArBarrelSampling

Make the arrays previously defines in LArBarrelSampling.icc const and move them into a header file. The conversion from the index-based initialization was done using a sed script. So the values should all be identical to before.

Also make the AccMap and PsMap const singletons. The only non-const functions are Reset and SetDirectory which are not used anywhere in athena. If they are needed in standalone code, one should use a const_cast if this is known to be safe.