Re-target for ES.Next (#3901)

A list of changes:
- 'es2015-subset' profile is deprecated, and an 'es.next' profile is added.
- The default profile is changed to 'es.next'
- Renamed the JERRY_ES2015 guard to JERRY_ESNEXT
- Renamed JERRY_ES2015_BUILTIN_* guards to JERRY_BUILTIN_*
- Moved es2015 specific tests to a new 'es.next' subdirectory
- Updated docs, targets, and test runners to reflect these changes

Resolves #3737.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

tests/jerry/es.next/class-inheritance-core-8.js

@@ -0,0 +1,85 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ var A = Array;
+ var order = 0;
+
+ function f () {
+   order++;
+
+   return function () {
+     return A;
+   }
+ }
+
+ var B = class extends f ()() {
+   constructor () {
+     assert (++order === 2);
+     eval ("eval ('super (1, 2, 3, 4)')");
+     try {
+       super (1, 2, 3, 4, 5)
+       assert (false);
+     } catch (e) {
+       assert (e instanceof ReferenceError)
+     }
+
+     assert (this.g ()()()() === 10);
+     assert (eval ("eval ('this.g ()')()")()() === 10);
+     assert (eval ("eval ('this.g ()')")()()() === 10);
+     assert (eval ("eval ('this.g ()()()')")() === 10);
+     assert (eval ("eval ('this.g')")()()()() === 10);
+     this.push (5);
+     assert (this.length === 5)
+     eval ('this.push (6)');
+     assert (this.length === 6);
+     eval ("eval ('this.push (7)')");
+     this.j = 6;
+     return;
+   }
+ }
+
+ var C = class extends B {
+   g () {
+     return function () {
+       return () => {
+         return 10;
+       }
+     }
+   }
+ }
+
+ var D = class D extends C {
+    constructor () {
+      super ();
+      this.k = 5;
+      return
+    }
+
+    g () {
+      return eval ('super["g"]');
+    }
+ }
+
+ assert (order === 1);
+
+ var d = new D;
+ assert (d.length === 7);
+ assert (d.k === 5);
+ assert (d.j === 6);
+ assert (d instanceof D);
+ assert (d instanceof C);
+ assert (d instanceof B);
+ assert (d instanceof f ()());
+ assert (JSON.stringify (d) === "[1,2,3,4,5,6,7]");