Move tether_utils into utils folder

This is no-op refactoring to move tether_utils into
a dedicated folder for utilities.

Test: m connectivity_multi_devices_snippet && \
      atest CtsConnectivityMultiDevicesTestCases:ConnectivityMultiDevicesTest
Bug: 345110845
Change-Id: I1df277570d3295e9ac5307f92e0a338481e3f732
3 files changed