Add test cases for drop counters ARP filter

This CL covers the following counters:
- DROPPED_ARP_V6_ONLY
- DROPPED_ARP_NON_IPV4
- DROPPED_ARP_UNKNOWN
- DROPPED_ARP_REPLY_SPA_NO_HOST
- DROPPED_GARP_REPLY

Test: atest NetworkStackTests:com.android.networkstack.android.net.apf.ApfFilterTest
Change-Id: Ic30c1658dbb9260b09322a3233c55bc628d87646
1 file changed