Modernize PrVeloUT, PrUTMagnetTool, PrTableForFunction

• prefer std::clamp(x,y,z) over std::min(std::max(x,y),z),
• prefer constexpr
• prefer static functions
• prefer inherited constructor
• prefer template deduction guides
• prefer LHCb::span over std::array as function argument
• prefer std::array over C-style array
• static_assert over assert