This deprecates all callables that are accepted by
call_user_func($callable) but not by $callable(). In particular:
"self::method"
"parent::method"
"static::method"
["self", "method"]
["parent", "method"]
["static", "method"]
["Foo", "Bar::method"]
[new Foo, "Bar::method"]
RFC: https://wiki.php.net/rfc/deprecate_partially_supported_callables
Closes GH-7446.
While parent:: should inherit the called scope, it should only do
so if it is compatible. If there is no called scope, or it is not
a subtype of the scope, we should fall back to the scope.
