Replace PackageManager @hide APIs

ConnectivityService is using
PackageManager#getApplicationInfoAsUser() to get application
info but this API is not able to call after CS becomes a
mainline module. Thus, replace it with formal API.

Bug: 170593746
Test: atest FrameworksNetTests
Test: atest CtsNetTestCasesLegacyApi22
Change-Id: Idd1269aa50e234801583097bb6f40b099bab8fba