refactor: TetherIngress becomes TetherDownstream6 (and friends) am: 770e0a7a8f am: 14583198a0

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/1554238

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I377e4c9f63f28f5b4918da29a36719f566359e2a
tree: 5a35ebd0224a8aa60a61a2a1b9219b1387475b10
  1. framework/
  2. tests/
  3. Tethering/
  4. .gitignore
  5. OWNERS
  6. PREUPLOAD.cfg
  7. TEST_MAPPING