Improve the definition of the stability of JS components.

(cherry picked from commit b2e8c46)

Author: ansalond

graal-js/mx.graal-js/mx_graal_js.py

@@ -325,7 +325,7 @@ def is_included(path):
     ],
     boot_jars=['graal-js:GRAALJS_SCRIPTENGINE'],
     installable=True,
-    supported=True,
+    stability="supported",
 ))
 
 def verify_ci(args):

graal-nodejs/mx.graal-nodejs/mx_graal_nodejs.py

@@ -623,7 +623,7 @@ def mx_post_parse_cmd_line(args):
     ],
     has_polyglot_lib_entrypoints=True,
     installable=True,
-    supported=True,
+    stability="supported",
 ))
 
 # pylint: disable=line-too-long