!act #15626 expose DatagramChannel creation in SocketOption

Fixes #15626
It seems to be a good idea to externalize the default to `ChannelCreator` but only until `ChannelCreator` has only one method. Otherwise user overriding only one of the `ChannelCreator` methods will get surprising results, because default `ChannelCreator` implementation would have side-effects.

I presume `ChannelCreator` can have more methods in the future (e.g. openSocketServerChannel) therefore default `ChannelCreator` should stay without side-effects.