Update connectivity TEST_MAPPING

 - Move Tethering TEST_MAPPING up one level to merge with the general
   Connectivity TEST_MAPPING. This allows running the tethering tests
   on any connectivity change.
 - Move TetheringIntegrationTests from postsubmit to presubmit
 - Add TetheringCoverageTests to mainline-postsubmit, so it can be
   added to mainline-presubmit later.
 - Import NetworkStack tests so that they are run on any connectivity
   change.

TetheringIntegrationTests were continuously green in postsubmit.

Bug: 187946226
Original-Change: https://android-review.googlesource.com/1713468
Merged-In: Ibf05ad64b02c563930ba0f01eb91331b295fe505
Change-Id: Ibf05ad64b02c563930ba0f01eb91331b295fe505
Test: Treehugger needed to test TEST_MAPPING files
2 files changed