Restoration Mask hardcode definitions

[plazzari]

@gbolzon The following code in domrea

  https://github.com/inogs/ogstm/blob/17-integration-with-fabm/src/IO/domrea.f90#L199-L226

should be removed, and nudging variables should be automatically defined considering BC namelists.
The current code version valid for BFMv5.3 makes difficult the multimodel approach.