This makes it possible to initialize_clone to correctly not freeze
internal state if the freeze: false keyword is passed to clone.
If clone is called with freeze: true or no keyword, do not pass
a second argument to initialize_clone to keep backwards
compatibility.
This makes it so that external libraries that override
initialize_clone but do not support the freeze keyword will fail
with ArgumentError if passing freeze: false to clone. I think that
is better than the current behavior, which succeeds but results in
an unfrozen object with frozen internals.
Fix related issues in set and delegate in stdlib.
Fixes [Bug #14266]
04eb7c7e46