Description of problem: Currently NB DB ACL changes trigger recomputes of the northd and lflow I-P nodes in ovn-northd. That's costly and can be avoided if we incrementally process the ACL changes in the lflow node. This depends on port groups being incrementally processed (bug 2228162) because ACLs can be applied on port groups too.
Patch that removes the explicit dependency between NB.ACLs/NB.Meters and the northd incremental processing node: https://patchwork.ozlabs.org/project/ovn/list/?series=369118&state=* It doesn't actually fully implement I-P for ACLs or Meters but it's an important first step that already reduces the performance impact when adding new ACLs/Meters because the northd node doesn't need to perform a full recomputation.
V2 patch that moves NB.ACLs and NB.Meters out of the northd I-P node: https://patchwork.ozlabs.org/project/ovn/list/?series=369253&state=*