Draft: switch for maxEcell decorator arguments for run 2 vs run 3

This switch allows for maxEcell decorator tool to borrow CellLinks() from nearby Egamma clusters for LRT collection in the case of a Run 2 reprocessing, and accesses the CellLinks() directly for Run 3. See [!52293 (merged)] and [!52256 (merged)] for more info. Tagging @jburzyns as he is working reformatting LLP1 and @longjon as an interested party. Please let me know if there is different syntax/style I should adopt before removing the draft tag.