Give foreign objects a foreign class composed of their interop traits

* Done:
  isNull() -> NoneType
  hasArrayElements() -> list
  hasHashEntries() -> dict
  isException() -> BaseException
* See the full mapping in GetForeignObjectClassNode.Trait.
* Test priority for attribute lookup on foreign objects.

Author: eregon

graalpython/com.oracle.graal.python.test.integration/src/com/oracle/graal/python/test/integration/interop/JavaInteropTest.java

@@ -584,7 +584,7 @@ public void javaStringsAndPythonStrings() throws IOException {
             Map<String, String> source = Map.of("source", "foo");
             context.getBindings("python").getMember("enrich").execute(source);
             assertEquals("" +
-                            "<class 'foreign'>\n" +
+                            "<class 'polyglot.ForeignDict'>\n" +
                             "True\n" +
                             "True\n", out.toString("UTF-8"));
         }