Remove unused fields and simplify logic in WSDL parser classes

- Deleted redundant `referencingSchema` field in `AbstractIncludeImport`.
- Removed `hasLocalName` method from `WSDLElement`.
- Simplified lambda usage in `Operation` for better readability.

Author: predic8

core/src/main/java/com/predic8/membrane/core/util/wsdl/parser/Operation.java

@@ -85,7 +85,7 @@ private List<Message> getMessagesByDirection(Node node, Direction direction) {
                     continue;
                 }
                 ctx.getDefinitions().findMessage(resolveQName(messageAttr, io).getLocalPart())
-                        .ifPresent(m -> result.add(m));
+                        .ifPresent(result::add);
             }
         }
         return result;

core/src/main/java/com/predic8/membrane/core/util/wsdl/parser/WSDLElement.java

@@ -92,8 +92,4 @@ protected static boolean isWSDLElement(Node node) {
     protected static boolean isXSDElement(Node node) {
         return node.getNodeType() == ELEMENT_NODE && XSD_NS.equals(node.getNamespaceURI());
     }
-
-    protected boolean hasLocalName(QName qn) {
-        return qn.getLocalPart().equals(name);
-    }
 }

core/src/main/java/com/predic8/membrane/core/util/wsdl/parser/schema/AbstractIncludeImport.java

@@ -23,7 +23,6 @@
 public abstract class AbstractIncludeImport extends WSDLElement {
 
     protected String schemaLocation;
-    protected Schema referencingSchema;
     protected Schema schema;
 
     public AbstractIncludeImport(WSDLParserContext ctx, Node node) {