Move kernelToTag to NetworkStatsFactory. am: adab7b1cc3 am: 4f3022fa09 am: a2af9dbf3d

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1964913

Change-Id: Ia30f60f23f8ab486ea948a470c84fb5fa1ab2971