Implement math for 2D measurements

To deal with the projection and filtering of 2D measurements in Rec, the corresponding math (Filter, Similarity transforms) for 2x5 projection matrices is implemented in the LHCb math kernel.

To match interface calls in Rec, this MR should be considered in line with Rec!2485 (merged) and Alignment!205 (merged)

Event/TrackEvent/Event/TrackTypes.h

@@ -24,13 +24,18 @@
 #include "GaudiKernel/GenericMatrixTypes.h"
 #include "GaudiKernel/GenericVectorTypes.h"
 #include "GaudiKernel/SymmetricMatrixTypes.h"
+#include <variant>
+
+// Should put into GaudiKernel/GenericMatrixTypes.h
+namespace Gaudi { typedef ROOT::Math::SMatrix<double, 2, 5> Matrix2x5; } ///< Generic 2x5 matrix (double)
 
 namespace Gaudi {
   // NB : Please remember to give a simple doxygen comment for each tyedef
   using TrackVector           = Vector5;      ///< Vector type for Track
   using TrackSymMatrix        = SymMatrix5x5; ///< Symmetrix matrix type for Track
   using TrackMatrix           = Matrix5x5;    ///< Matrix type for Track
-  using TrackProjectionMatrix = Matrix1x5;    ///< Projection matrix type for Track
+  using TrackProjectionMatrix1D = Matrix1x5;    ///< Projection matrix type for Track
+  using TrackProjectionMatrix2D = Matrix2x5;
 
 } // namespace Gaudi