xAOD::EventAuxInfo_v3, 22.0-mc20 branch (2021.12.07.)

This is a (partial) cherry-pick of !48676 (merged). Continuing with fixing ATLASRECTS-6707.

I started trying to update the reference files in the branch already, but ran into some technical issues with q221 that I can't yet explain. 😦 So I thought I would just let the CI chew this as well, and tell me what are the failing tests in its current state.