WifiService: Plumb the oem private flag for suggestions

This is treated similarly to oem paid suggestions. However, they are
lower priority than oem paid suggestions for network selection purposes.

Bug: 169413079
Test: atest com.android.server.wifi
TesT: adb shell cmd wifi add-suggestion blahblah open -p
Change-Id: I916c50445492da4f70359d935f4221df5bacfa68
32 files changed
tree: 0fb202c1bbe9cd84500580141c156b3def1d5cff
  1. apex/
  2. service/
  3. metrics_pdd_hook.py
  4. PREUPLOAD.cfg