Make EIP node update event handling better

[tssurya]

What is this issue about?

See #4265 (comment) for details
But TL;DR is that there are occassions when we don't want to do extra computing for every node update then coupling that together with say the fact that node updates for two different nodes in two different threads can happen in parallel that try to create the same ovn constructs can also cause race issues. In the past we have solved this using (1) waitops hack 2) mutexes 3) OVNK specific caches like what @trozet ^ is suggesting above 4) ensuring we call the create from a global space and avoid the threads racing all together if possible

I went with 2 for now, but probably 3 is the better way to do specially if in the future we have more cases like we do in case of node events.