This MR fixes a bug in the MET reconstruction - currently for example it takes a link from an electron to FE and looks up the FE index. Then it assumes that index is valid in the global FE container - that assumption is invalid. The MR fixes this by creating new links between global FE and electron/photon/muon/taus and then updates the MET c++ code to use these links.
Configuration is added to remove these new global links, and associated variables, from the AOD/ESD - the global FE are not written to either ESD or AOD, so any associated decorations related to this would be useless.
This MR should not violate FT0V in that the AOD contents will not change. The ESD contents, which includes MET, will change because the MET output changes. Therefore eventually when this goes to master it is expected the MET content in PHYS and PHYSLite will change @jcatmore. Can you provide an example Reco_tf command I can use to check if any additional derivation specific config changes are required (this will be the case, if neither RecExCommon nor RecoSteering are used - we would find MET crashes when it does not find these new global links)? Given we don't run derivations in 22.0, I would propose to address this in a separate MR for master once this sweeps there.