* Use public stable API to load certificates from keystore.
* Also use grants to allow racoon to use keystore keys without
special exceptions in keystore.
* Use LegacyProfileStore instead of Keystore for storing VPN profiles.
Bug: 175068876
Bug: 171305607
Test: atest android.net.cts.Ikev2VpnTest
atest android.net.cts.IpSecManagerTest
atest com.android.server.connectivity.VpnTest
atest com.android.server.ConnectivityServiceTest
Change-Id: I27975113896ea137260a9f94a34fb1c3ca173fe3
4ba2f0c690