WifiNetworkSuggestion: Don't store packageName/uid

The service will stamp the uid, package name of individual suggestions
when it creates its internal representation for each suggestion (i.e
ExtendedWifiNetworkSuggestion). This is to avoid using an @hide API
inside WifiNetworkSuggestion to stamp the uid/package name of the app
using a retrieved context.

Bug: 144102365
Test: atest android.net.wifi
Change-Id: I86651c76053b613d9eb9dc95ab51b07b11f23f16