Connectivity metrics: simplify ConnectivityMetricsEvent

Now that ConnectivityMetricsEvent is only used for core networking
metrics and is not @SystemApi anymore, remove unused fields and prepare
for additional new fields.

Test: updated unit tests, $ runtest frameworks-net passes
Bug: 34901696
Change-Id: I15abad19981d491f16f2a3afe401f1e833079907

tests/net/java/com/android/server/connectivity/IpConnectivityMetricsTest.java

@@ -304,14 +304,15 @@ public class IpConnectivityMetricsTest extends TestCase {
     }
 
     static ConnectivityMetricsEvent expectedEvent(int timestamp) {
-        return new ConnectivityMetricsEvent((long)timestamp, 0, 0, FAKE_EV);
+        ConnectivityMetricsEvent ev = new ConnectivityMetricsEvent();
+        ev.timestamp = timestamp;
+        ev.data = FAKE_EV;
+        return ev;
     }
 
     /** Outer equality for ConnectivityMetricsEvent to avoid overriding equals() and hashCode(). */
     static void assertEventsEqual(ConnectivityMetricsEvent expected, ConnectivityMetricsEvent got) {
         assertEquals(expected.timestamp, got.timestamp);
-        assertEquals(expected.componentTag, got.componentTag);
-        assertEquals(expected.eventTag, got.eventTag);
         assertEquals(expected.data, got.data);
     }
 

tests/net/java/com/android/server/connectivity/MetricsTestUtil.java

@@ -28,7 +28,10 @@ abstract public class MetricsTestUtil {
     }
 
     static ConnectivityMetricsEvent ev(Parcelable p) {
-        return new ConnectivityMetricsEvent(1L, 0, 0, p);
+        ConnectivityMetricsEvent ev = new ConnectivityMetricsEvent();
+        ev.timestamp = 1L;
+        ev.data = p;
+        return ev;
     }
 
     static ConnectivityMetricsEvent describeIpEvent(Consumer<Parcel>... fs) {