De-guava BroadcastInterceptingContext and move it to testutils.

Removing the static dependency on guava reduces test compile time
by about 20 seconds on a Z840, thus substantially speeding up the
compile/test cycle.

Make FutureIntent public instead of package-private because it is
used directly by NetworkPolicyManagementServiceTest, which as of
this CL is now in a different package.

(cherry picked from commit 6a64dd2178)

Test: runtest frameworks-services -c com.android.server.ConnectivityServiceTest  # PASS
Test: runtest frameworks-services -c com.android.server.NetworkPolicyManagerServiceTest  # PASS
Test: runtest frameworks-services -c com.android.server.net.NetworkStatsServiceTest  # PASS
Test: runtest frameworks-services -c com.android.server.NetworkManagementServiceTest  # Already failing.
Bug: 31479480
Change-Id: Ifab32c9214e9caab71dbf93b3d3ca88df6f49636

services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java

@@ -76,6 +76,7 @@ import android.util.Log;
 import android.util.LogPrinter;
 
 import com.android.internal.util.WakeupMessage;
+import com.android.internal.util.test.BroadcastInterceptingContext;
 import com.android.internal.util.test.FakeSettingsProvider;
 import com.android.server.connectivity.NetworkAgentInfo;
 import com.android.server.connectivity.NetworkMonitor;