Implement realm object and support realms for built-ins and JS functions (#4354)

- Type for realm objects is introduced (ecma_global_object_t)
- Realm reference is added to built-in objects and ECMAScript functions
- Resolving built-ins, global environments, and scopes require realm object
- Unnecessary global object accesses are removed from the code

Missing: external functions and static snapshot functions have no realm reference

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

tests/jerry/es.next/realms2.js

@@ -0,0 +1,48 @@
+// 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.
+
+// Test1: realm cannot be gc-ed until it is referenced
+
+function f1() {
+  var ev = createRealm().eval
+
+  gc()
+
+  try {
+    ev("5 +")
+  } catch (e) {
+    assert(e instanceof ev("this").SyntaxError)
+    assert(!(e instanceof SyntaxError))
+  }
+}
+f1()
+
+// Test2: built-ins cannot be gc-ed until the realm exists
+
+function f2() {
+  var realm = createRealm()
+
+  var str = new realm.String("A");
+  // Assign a property to String.prototype
+  Object.getPrototypeOf(str).myProperty = "XY"
+
+  str = null
+  // No reference to String.prototype
+  gc()
+
+  str = new realm.String("A")
+  assert(Object.getPrototypeOf(str).myProperty === "XY")
+  assert(realm.String.prototype.myProperty === "XY")
+}
+f2()