Handle NO_MATCH in VisitorState#reportMatch instead of `Scanner

This fix prevents reports such as the following, which are hard to debug
for users:
```
[INFO] /path/to/some/File.java: [<no match>] <no match>
   (see <no match>)

Fixes #1609

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=311378177

check_api/src/main/java/com/google/errorprone/VisitorState.java

@@ -264,6 +264,9 @@ public ErrorProneOptions errorProneOptions() {
   }
 
   public void reportMatch(Description description) {
+    if (description == null || description == Description.NO_MATCH) {
+      return;
+    }
     // TODO(cushon): creating Descriptions with the default severity and updating them here isn't
     // ideal (we could forget to do the update), so consider removing severity from Description.
     // Instead, there could be another method on the listener that took a description and a

check_api/src/main/java/com/google/errorprone/scanner/Scanner.java

@@ -121,9 +121,6 @@ protected Set<? extends Name> getCustomSuppressionAnnotations(VisitorState state
   }
 
   protected void reportMatch(Description description, VisitorState state) {
-    if (description == null || description == Description.NO_MATCH) {
-      return;
-    }
     state.reportMatch(description);
   }
 

core/src/test/java/com/google/errorprone/bugpatterns/time/StronglyTypeTimeTest.java

@@ -245,6 +245,19 @@ public void fieldNotPrivate_noMatch() {
         .doTest();
   }
 
+  @Test
+  public void unusedField_noMatch() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            "import java.io.Serializable;",
+            "class Test implements Serializable {",
+            "  private static final long serialVersionUID = 1L;",
+            "}")
+        .expectNoDiagnostics()
+        .doTest();
+  }
+
   @Test
   public void whenJodaAndJavaInstantUsed_fullyQualifiesName() {
     refactoringHelper