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

docs/02.API-REFERENCE.md

@@ -141,6 +141,8 @@ Possible compile time enabled feature types:
  - JERRY_FEATURE_SET - Set support
  - JERRY_FEATURE_WEAKMAP - WeakMap support
  - JERRY_FEATURE_WEAKSET - WeakSet support
+ - JERRY_FEATURE_BIGINT - BigInt support
+ - JERRY_FEATURE_REALM - realm support
 
 *New in version 2.0*.
 
@@ -5969,6 +5971,38 @@ jerry_create_undefined (void);
 - [jerry_release_value](#jerry_release_value)
 
 
+## jerry_create_realm
+
+**Summary**
+
+Creates a `jerry_value_t` representing a new global object.
+
+**Prototype**
+
+```c
+jerry_value_t
+jerry_create_realm (void);
+```
+
+- return value - realm object value
+
+**Example**
+
+```c
+{
+  jerry_value_t realm_value = jerry_create_realm ();
+
+  ... // usage of the value
+
+  jerry_release_value (realm_value);
+}
+```
+
+**See also**
+
+- [jerry_release_value](#jerry_release_value)
+
+
 # General API functions of JS objects
 
 ## jerry_has_property