POC for defunct route options

[dantleech]

The aim of this POC PR is to explore the possiblity passing options to the defunct route handlers - the use case being allowing the redirect HTTP code to be passed to the adapter which creates the redirect route.

Intitially I tried to avoid BC breaks, but the requirement to add $options to the handleDefunctRoutes method breaks any chance of this. The role of the new ConfigurableInterface is therefore up for debate.

[wouterj]

Do you think there are going to be more settings than the HTTP code? Otherwise, I'd prefer to not use the options resolver and just pass a config value to the constructor of LeaveRedirectDefunctRouteHandler.

[dantleech]

There was a reason -- iirc it might have been that the HTTP code is not a DI config, is is metadata.

[wouterj]

I propose to remove the ConfigurableInterface and add a new BC break. However, the current PR doesn't do anything, as the http code option isn't used anywhere in the code.