Move NetworkStackTest to common folder to support cts

Bug: 154775373
Test: atest CtsNetTestCasesLatestSdk:android.net.NetworkStackTest
      on both Q and R device
Change-Id: I91be50077749c2d357ee6f292fe4e127d1e46b8b
Merged-In: I91be50077749c2d357ee6f292fe4e127d1e46b8b
(cherry picked from commit fc228152322b4512200a65ebff9e6f3b8fb2594d)
1 file changed