Dynamic input shape option for MLServiceAlg

Add MLServiceAlg option (MLServiceAlg_2DTo1D_Relation1D and MLServiceAlg_2DTo1D_Relation2D) with dynamic input dimension in relation table format.

Typical use case is flavour tagging or isolation where one has a Particle object (FROM) that could be related to an unknown number of Particles (TO) and one wants to infer something from those relations with a fixed set of features per TO object to an output (e.g. of a classifier) per FROM object.

needs LHCb!5459

application example / test in Moore!5572