Add an OWNERS_core_networking_xts for CTS/GTS/... and use it. am: 7aac4ad2f7 am: 95edb88396

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/1952105

Change-Id: Iabe810026c7d2ae9b6110b6be6f2acb8090a37cc