Merge "[Thread] add private API ThreadNetworkSpecifier" into main am: 594a9a8cfa

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3313064

Change-Id: I3e78ac05271d47f76f30e0ccd626f980208a3b37
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>