Add NetworkStackTests / NetworkStackNextTests to mainline-presubmit am: 0e6d63fe am: e6781b7b am: 81c798d8 am: 1b8b3615

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1504413

Change-Id: I0d1cafddd2d24d050897877982ab3de12b420017