SEC-2326: CsrfRequestDataValueProcessor implements RequestDataValueProcessor

Previously there was unecessary complexity in CsrfRequestDataValueProcessor
due to the non-passive changes in RequestDataValueProcessor. Now it simply
implements the interface with the methods for both versions of the interface.
This works since linking happens at runtime.

web/src/test/java/org/springframework/security/web/servlet/support/csrf/CsrfRequestDataValueProcessorTests.java

@@ -126,7 +126,7 @@ public class CsrfRequestDataValueProcessorTests {
         Map<String,String> expected = new HashMap<String,String>();
         expected.put(token.getParameterName(),token.getToken());
 
-        RequestDataValueProcessor processor = CsrfRequestDataValueProcessor.create();
+        RequestDataValueProcessor processor = new CsrfRequestDataValueProcessor();
         assertThat(processor.getExtraHiddenFields(request)).isEqualTo(expected);
     }
 }