Remove ES_NEXT macro (#4915)

- remove all '#JERRY_ESNEXT' macro
- remove 5.1 build profile, update test runner accordingly (Note: all builtins are turn on by default)
- move tests from tests/jerry/esnext into tests/jerry, concatenate files with same names
- add skiplist to some snapshot tests that were supported only in 5.1
- fix doxygen issues that were hidden before (bc. of es.next macro)

Co-authored-by: Martin Negyokru negyokru@inf.u-szeged.hu
JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/jerry/let5.js

@@ -0,0 +1,35 @@
+/* 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.
+ */
+
+let arr = [];
+
+for (var a = 0; a < 10; a++)
+{
+  let j = a;
+  var f;
+
+  {
+    f = function () { return j; }
+
+    let j = (a & 0x1) ? a + 10 : a + 100;
+  }
+
+  arr[j] = f;
+}
+
+for (var a = 0; a < 10; a++)
+{
+  assert (arr[a]() == ((a & 0x1) ? a + 10 : a + 100))
+}