ATLASEG-329: AOD fix for missing cells in egamma cluster core due to timing cut

Details are given in ATLASEG-329

The timing cut introduced in topo-cluster building is too tight for egamma, and can create holes in clusters. This creates non-linearity in the energy measurement. One can try to recover the energy lost from these missing cells since we store 7x11 cell clusters around each egamma cluster in AOD. This MR tries that (code from @gunal) and stores the energy in the missing cells in layers 2 and 3 as decorations to all electrons and all photons.

This will be completed in another correction in the final energy computation (the decorations will be added to layer 2 and 3 energies, prior to MVA energy computation) (!64748 (merged))

Tagging @ludovica @turra @gunal @christos @mungo