Modernize UTDet

• prefer pass-by-value for small objects
• remove redundant dynamic_cast
• drop redundant const qualifiers
• prefer [[maybe_unused]] over #ifdef NDEBUG
• include the relevant header
• move DeUTSector::Status conversion to/from string to DeUTSector
• add functions needed to support Gaudi::PropertyDeUTSector::Status
• move the functions in UTDetFun to the .cpp files which use them, and retire UTDetFun.h
• make the member functions of UTNames static

must be applied in conjunction with Lbcom!575 (merged)