Re-target for ES.Next (#3901)

A list of changes:
- 'es2015-subset' profile is deprecated, and an 'es.next' profile is added.
- The default profile is changed to 'es.next'
- Renamed the JERRY_ES2015 guard to JERRY_ESNEXT
- Renamed JERRY_ES2015_BUILTIN_* guards to JERRY_BUILTIN_*
- Moved es2015 specific tests to a new 'es.next' subdirectory
- Updated docs, targets, and test runners to reflect these changes

Resolves #3737.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

jerry-core/parser/js/common.h

@@ -74,9 +74,9 @@ typedef enum
   LEXER_FLAG_SOURCE_PTR = (1 << 2), /**< the literal is directly referenced in the source code
                                      *   (no need to allocate memory) */
   LEXER_FLAG_LATE_INIT = (1 << 3), /**< initialize this variable after the byte code is freed */
-#if ENABLED (JERRY_ES2015)
+#if ENABLED (JERRY_ESNEXT)
   LEXER_FLAG_GLOBAL = (1 << 4), /**< this local identifier is not a let or const declaration */
-#endif /* ENABLED (JERRY_ES2015) */
+#endif /* ENABLED (JERRY_ESNEXT) */
 } lexer_literal_status_flags_t;
 
 /**