Updated Athena to LCG96, tdaq-08-03-00 and tdaq-common-03-04-00.
We will separately update the default version in atlasexternals, and then can remove the override here.
Walter tested LCG96 already, so we don't expect issues (but I have to confess I'm relying on the CI here, so let's not accept this until we're sure it's okay).
Also cherry-picked / implemented changes from !24663 (closed) by Walter (modified one change as per the suggestion by Frank on that MR).