Add bpf forwording packet count test

- Add dumpsys option to dump stats map in BpfCoordinator
- Add stats test to check bpf forwording packet count in
  EthernetTetheringTest

Bug: 227159997
Test: atest TetheringCoverageTests
Change-Id: I177787ed0c28ebe137ff1431f40a23b1e4b22a19
2 files changed