datapath: Refactor ARP handling from inout app

[pshelar]

Create separate module to handle ARP handling
verification:
Run unit test and integ test after rector is done.

[sebathomas]

@pshelar Can you give a few more details about this task? Which ARP handling should be extracted to a separate module?

Is it about the ArpController or ARP handling in one of the other parts of pipelined? It might also be related to #12495, I see there are some reference to ARP in the new EgressController.

[pshelar]

I am referring to ARP probes : _get_gw_mac_address_v4(), _get_gw_mac_address_v6(), etc:

magma/lte/gateway/python/magma/pipelined/app/inout.py

Line 510 in de09125

def _get_gw_mac_address_v4(self, ip: IPAddress, vlan: str = "") -> str: