Add NATT keepalive resources and methods into IpSecService

This change adds a new NATTKeepalive resource type, along with the
associated allocation/deallocation. Additionally, this change allows
ReferenceCountedResource(s) to not be binder-linked, to allow the
ConnectivityService to verify ownership and allocate a NattKeepalive
without double-registering for binder-death notifications.

Bug: 125517194
Test: IpSecService frameworks tests ran
Change-Id: I8293f79940ad57dabb6f2b9de5e334d06b869443

core/java/android/net/IIpSecService.aidl

@@ -72,4 +72,8 @@ interface IIpSecService
             int tunnelResourceId, int direction, int transformResourceId, in String callingPackage);
 
     void removeTransportModeTransforms(in ParcelFileDescriptor socket);
+
+    int lockEncapSocketForNattKeepalive(int encapSocketResourceId, int requesterUid);
+
+    void releaseNattKeepalive(int nattKeepaliveResourceId, int ownerUid);
 }