Add the NotDeletable, OperationsNotDeletable IDL attributes

Add the NotDeletable, OperationsNotDeletable IDL attributes
https://bugs.webkit.org/show_bug.cgi?id=122217

Reviewed by Darin Adler.

Before adjusting the JSC bindings generator to enforce configurable operations and thus conform to the
WebIDL specification in this regard, two no-op attributes are introduced that will preserve the current
behavior of operations being non-configurable.

All the relevant interfaces will be annotated with the OperationsNotDeletable attribute first. After the
generator is properly modified, this attribute will be removed from the interfaces after checking that
the operations' configurability also matches the configurability of operations in other browser engines
and that the change introduces no regressions in tests.

The NotDeletable attribute will be used as required to annotate operations that should stay
non-configurable for backwards compatibility or cross-browser compatibility.

* bindings/scripts/IDLAttributes.txt:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@156831 268f45cc-cd09-0410-ab3c-d52691b4dbfc