Merge "[Thread] introduce TestTunNetworkUtils and use it in existing test cases" into main am: 7175f59956

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3346199

Change-Id: I059c84982245aa4c3e2a8b779857ab3fd9627330
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>