Merge changes I26b58953,I236b6c5e,I2989dd6c,I96667bd0,I1f0f1972

* changes:
  eliminate tethering stuff from bpf_shared.h
  OffloadUtils - drop support for tethering tc & xdp program attachment
  remove tether related helper functions from OffloadUtils.h
  remove netd_test NetdBpfTest.testBpfSkbChangeHeadAboveMTU()
  TetherController - remove everything related to TetherOffloadStats