Need CEL convenience function: inIpRange()

Currently, Envoy's CEL functions are essentially what the mainline CEL repo provides. However, as more use cases pile up, it may be worthwhile to add some additional convenience functions (where sensible) to make configuration & processing faster in Envoy.

In the case of this issue, the function being requested is inIpRange(). We have attributes that contain IP data (source.address, destination.address, etc.). Often times, a user wants to check if the IP is in a range. Its clunky and error prone to do this with string matches. So the request is to add an inIpRange() CEL function to Envoy whose semantics are like inIpRange(source.address, '9.9.9.0/24')

cc @kyessenov @tyxia