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/object-keys.js

@@ -88,3 +88,36 @@ props = Object.keys(o);
 assert(props.length === 2);
 assert(o[props[0]] === "OK");
 assert(o[props[1]] === "OK");
+
+var object = {};
+
+Object.defineProperties(object, {
+  a: {
+    value: "foo",
+    enumerable: false
+  },
+  b: {
+    value: "bar",
+    enumerable: true,
+    writable: false
+  }
+});
+
+var proxy = new Proxy(object, {
+  getOwnPropertyDescriptor: function(o, v) {
+    handlers.push("D");
+    return Object.getOwnPropertyDescriptor(o, v);
+  },
+  get: function(o, v) {
+    handlers.push("G");
+    return o[v];
+  }
+});
+
+var handlers = [];
+var keys = Object.keys(proxy);
+
+assert(keys.length === 1);
+assert(keys[0] === "b");
+assert(handlers.length === 2);
+assert(handlers.toString() === "D,D");