Backport various xAOD::EventInfo related updates to 21.0-mc16d
Backport various xAOD::EventInfo related updates to 21.0-mc16d. See ATLASSIM-4813 for more info.
Note for reviewers: these are all direct cherry-picks so unless CI fails, I do not plan to do any changes.
Covered MRs: https://gitlab.cern.ch/atlas/athenaprivate1/-/merge_requests/15794 !20005 (merged) !20788 (merged) !21828 (merged) !24967 (merged) !25385 (merged) !26617 (merged) !36264 (merged) !36363 (merged)