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/symbol-key-keyfor.js

@@ -0,0 +1,60 @@
+/* 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.
+ */
+
+try {
+  Symbol.for (Symbol('foo'));
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError)
+}
+
+var a = Symbol.for ('foo');
+var b = Symbol.for ('foo');
+
+assert (a === b);
+assert (a == b);
+
+assert (Symbol.keyFor (a) === 'foo');
+assert (Symbol.keyFor (b) === 'foo');
+
+// Test non-string arguments
+var c = Symbol.for (5);
+var d = Symbol.for (5.58);
+var e = Symbol.for ({});
+
+assert (Symbol.keyFor (c) === '5');
+assert (Symbol.keyFor (d) === '5.58');
+assert (Symbol.keyFor (e) === '[object Object]');
+
+// Test global symbol table
+var array = [];
+for (var i = 0; i < 15; i++) {
+  array[i] = Symbol.for ('foo' + i);
+
+  for (var j = 0; j < i; j++) {
+    assert (array[j] !== array[i]);
+  }
+}
+
+try {
+  Symbol.keyFor ('NonSymbolValue');
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError);
+}
+
+for (var i = 0; i < 15; i++) {
+  assert (Symbol.keyFor (array[i]) === ('foo' + i));
+}