bypass: use flow storage for bypass counter

bypass: use flow storage for bypass counter

There is a synchronization issue occuring when a flow is
added to the eBPF bypass maps. The flow can have packets
in the ring buffer that have already passed the eBPF stage.
By consequences, they are not accounted in the eBPF counter
but are accounted by Suricata flow engine.

This was causing counters to be completely wrong. This code
fixes the issue by avoiding the counter change in invalid
case.

To avoid adding 4 64bits integers to the Flow structure for the
bypass accounting, we use instead a FlowStorage. This limits the
memory usage to the size of a pointer.