Implement Symbol.matchAll (#4082)

The following methods were implemented:
- String.prototype.matchAll based on ECMA-262 v11, 21.1.3.12
- RegExp.prototype[@@matchAll] based on ECMA-262 v11, 21.2.5.8
- RegExp String Iterator Object based on 21.2.7

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

jerry-core/include/jerryscript-core.h

@@ -712,6 +712,7 @@ typedef enum
   JERRY_SYMBOL_TO_PRIMITIVE,         /**< @@toPrimitive well-known symbol */
   JERRY_SYMBOL_TO_STRING_TAG,        /**< @@toStringTag well-known symbol */
   JERRY_SYMBOL_UNSCOPABLES,          /**< @@unscopables well-known symbol */
+  JERRY_SYMBOL_MATCH_ALL,            /**< @@matchAll well-known symbol */
 } jerry_well_known_symbol_t;
 
 jerry_value_t jerry_get_well_known_symbol (jerry_well_known_symbol_t symbol);