rename Map and Filter test classes now that have moved to OnSubscribe (#4243)

Author: davidmoten

src/test/java/rx/internal/operators/OperatorFilterTest.java renamed to src/test/java/rx/internal/operators/OnSubscribeFilterTest.java

@@ -30,7 +30,7 @@
 import rx.observers.TestSubscriber;
 import rx.subjects.PublishSubject;
 
-public class OperatorFilterTest {
+public class OnSubscribeFilterTest {
 
     @Test
     public void testFilter() {

src/test/java/rx/internal/operators/OperatorMapTest.java renamed to src/test/java/rx/internal/operators/OnSubscribeMapTest.java

@@ -32,7 +32,7 @@
 import rx.schedulers.Schedulers;
 import rx.subjects.PublishSubject;
 
-public class OperatorMapTest {
+public class OnSubscribeMapTest {
 
     @Mock
     Observer<String> stringObserver;