Follow Rec!2977

This introduces the minimal changes for FunTuple to understand the optional return type of Functors::Optional<T>

Note that Rec!2977 (merged) does not yet change the behavior of e.g. MapRelInputToFunOuput. These Functors still return their constexpr invalid_value.

My proposal would be to merge Rec!2977 (merged) as is + this MR.
Then I can create a follow-up MR that removes the current usage of the constexpr invalid_value member to replace it with the new optional return type functionality.
But for that we also need to adapt FunTuple with the features to let us specify a default invalid value for a specific column in the tuple.

@amathad I am hoping you might have time to help with the latter? I already looked at FunTuple.cpp but wasn't sure where this should best be implemented.

Phys/FunTuple/src/FunTuple.cpp

@@ -50,6 +50,7 @@
 // ThOr functor
 #include "Functors/FunctorDesc.h"
 #include "Functors/IFactory.h"
+#include "Functors/Optional.h"
 
 // DetDesc
 #include "DetDesc/ConditionAccessor.h"
@@ -335,7 +336,7 @@ namespace LHCb {
       return StatusCode::SUCCESS;
     }
 
-    // make a map of type_index and function that calls fill function for all T and optional<T>
+    // make a map of type_index and function that calls fill function for all T and Functors::Optional<T>
     template <typename... T>
     auto make_map() {
       using Fun = StatusCode ( * )( const Tuples::Tuple&, const std::string&, const std::any& );
@@ -357,7 +358,7 @@ namespace LHCb {
               } );
         };
       };
-      ( add_if_invalid_exists( std::optional<T>{} ), ... );
+      ( add_if_invalid_exists( Functors::Optional<T>{} ), ... );
 
       // add map entry of type_index (std::map<std::string, T>) -> fill function
       auto add_map_val = [&m]( auto map ) {
@@ -1158,4 +1159,4 @@ void FunTupleBase<T>::update_counters( const unsigned int& field_indx, const uns
 DECLARE_COMPONENT_WITH_ID( FunTupleBase<LHCb::Particle::Range>, "FunTupleBase_Particles" )
 DECLARE_COMPONENT_WITH_ID( FunTupleBase<LHCb::MCParticles>, "FunTupleBase_MCParticles" )
 DECLARE_COMPONENT_WITH_ID( FunTupleBase<LHCb::Event::Composites>, "FunTupleBase_Composites" )
-DECLARE_COMPONENT_WITH_ID( FunTupleBase<LHCb::Event::ChargedBasics>, "FunTupleBase_ChargedBasics" )
\ No newline at end of file
+DECLARE_COMPONENT_WITH_ID( FunTupleBase<LHCb::Event::ChargedBasics>, "FunTupleBase_ChargedBasics" )