Rework Object's [[OwnPropertyKeys]] (#4001)

I've removed the ecma_op_object_get_property_names method, and implemented the following ones:
- ecma_op_object_own_property_keys: this is now the internal [[OwnPropertyKeys]] method
- ecma_op_object_enumerate: this is used for the for-in iterator
- ecma_object_sort_property_names: this is used for sorting the property names of an object
- ecma_object_list_lazy_property_names: this is for getting the lazy instantiated properties
- ecma_object_prop_name_is_duplicated: this is for checking if a given property is duplicated in an object

Also the for-in operation with Proxy object works with this patch, #3992 should be closed

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/jerry/es.next/proxy_own_keys.js

@@ -31,14 +31,6 @@ var handler = { ownKeys (target) {
 
 var proxy = new Proxy(target, handler);
 
-try {
-  // Array.prototype.sort
-  Array.prototype.sort.call(proxy);
-  assert(false);
-} catch (e) {
-  assert(e === 42);
-}
-
 try {
   // 19.1.2.14.4
   Object.keys(proxy);
@@ -63,6 +55,14 @@ try {
   assert(e === 42);
 }
 
+var handler = { ownKeys (target) {
+  return ["a"];
+}};
+
+var proxy = new Proxy(target, handler);
+var sort_result = Array.prototype.sort.call(proxy);
+assert(Object.keys(sort_result).length === 0);
+
 // test basic functionality
 var symA = Symbol("smA");
 var symB = Symbol("smB");
@@ -149,16 +149,18 @@ try {
 }
 
 // test with duplicated keys
-var target = { prop1: "prop1", prop2: "prop2"};
-var handler = {
+var p = new Proxy({}, {
 	ownKeys: function(target) {
-      return ["a", "a", "a"];
-    }
-};
+	  return ["foo", "foo"];
+	}
+});
 
-var proxy = new Proxy(target, handler);
-
-assert(JSON.stringify(Object.getOwnPropertyNames(proxy)) === '["a","a","a"]');
+try {
+  Object.keys(p);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
 
 // test with lots of keys
 var keyslist = [];
@@ -240,4 +242,4 @@ var handler = {
 var proxy = new Proxy(object, handler);
 
 assert(Object.keys(proxy).length === 1);
-assert(Object.keys(proxy)[0] === "b");
+assert(Object.keys(proxy)[0] === "b");