r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are still not MPSAFE (or already are but aren’t properly marked). Use it in preparation for a general review of all nodes.
This is non-functional change that adds annotations to SYSCTL_NODE and SYSCTL_PROC nodes using one of the soon-to-be-required flags.
Mark obvious cases as MPSAFE.
This review covers all parts not specified otherwise in reviews D23625 to D23640.
All entries that haven't been marked as MPSAFE before are by default marked as NEEDGIANT.