Modernize CaloFuture

• follow changes in match interface -- no need to add std::optional around a type which has a recognizable invalid state
• put tools/algorithms in namespace Calo::Future
• prefer ToolHandles
• remove use of redundant futuredetails::to_string
• prefer free-standing functions over member functions which do not interact with their hosting class
• remove some unused code
• prefer std::is_base_of_v<...> over std::is_base_of<...>::value
• prefer STL algorithms over raw loops

Must be applied in conjunction with LHCb!1990 (merged)