Streamline FunctionalFlavourTagging algorithm implementations

• amalgamate component header files into their source files
• drop unnecessary header includes
• drop commented out and duplicated code
• pick up algorithm interface from LHCb::Algorithm instead of Gaudi::Functional
• prefer Particle::Range over Particles
• make constants static constexpr
• declare CloneStatus as a 'strong' enum
• prefer multiplication over division
• replace if (value) return true ; else return false by return value;
• move cloneCategory from TaggingHelperTool to TaggingHelper as it does not access any members of TaggingHelperTool
• move bestPVUnbiased from TaggingHelper to FunctionalSSPionTagger as it is the only place where it is used
• prefer std::accumulate over raw for loops
• optimize computation of dPhi (avoid multiple trigonometric functions and some divisions)
• avoid use of essentiallyEqual in comparison used for sorting as it can give unexpected (and wrong) results (see https://godbolt.org/z/sv8oWEvYe for a demonstration) -- given that it violates one of the axioms sort relies on, this is formally 'undefined behaviour' and could even result in sort ending up going out-of-bounds and crashing (very unlikely in practice though)