Add NetworkStack to framework-connetivity and framework-tethering impl lib visibility am: e7cae17b3a

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3259762

Change-Id: If1a9a3c694c08ab43b24c355d7388576c01e4158
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>