Add java class for Ingress discard bpf map key value Cherry-pick of aosp/2795708 to backport VPN security fix to non-mainline U devices. Bug: 193031925 Test: TH Merged-In: Ic9ac423aee2a8fb9709b0acf012ec57cdfa019f9 Change-Id: Ib403099df5cefa3cbad52e3fd568b1a5047adcd4