[MNG-8601] Add type test-java-source type (#2136)

Similar to java-source type, but for tests sources.

---

https://issues.apache.org/jira/browse/MNG-8601

Author: cstamas

api/maven-api-core/src/main/java/org/apache/maven/api/Type.java

@@ -122,6 +122,11 @@ public interface Type extends ExtensibleEnum {
      */
     String TEST_JAR = "test-jar";
 
+    /**
+     * Artifact type name for a JAR file containing test sources.
+     */
+    String TEST_JAVA_SOURCE = "test-java-source";
+
     /**
      * Returns the dependency type id.
      * The id uniquely identifies this <i>dependency type</i>.

impl/maven-impl/src/main/java/org/apache/maven/impl/resolver/type/DefaultTypeProvider.java

@@ -54,6 +54,7 @@ public Collection<DefaultType> types() {
                         false,
                         JavaPathType.CLASSES,
                         JavaPathType.PATCH_MODULE),
+                new DefaultType(Type.TEST_JAVA_SOURCE, Language.JAVA_FAMILY, "jar", "test-sources", false),
                 new DefaultType(Type.MODULAR_JAR, Language.JAVA_FAMILY, "jar", null, false, JavaPathType.MODULES),
                 new DefaultType(Type.CLASSPATH_JAR, Language.JAVA_FAMILY, "jar", null, false, JavaPathType.CLASSES),
                 // j2ee types