Níma: remove default config in webserver

[tomas-langer]

Currently webserver uses configuration obtained through Config.create() even when it is later explicitly set.
We should remove this and expect users to provide configuration to us through APIs (as we have in reactive).

We may use some global configuration instance configured statically (see Nima.config()), though that should return an Optional<Config>, so we ignore it unless configured by user. This must also align correctly with config driven services when Pico is used.

[tomas-langer]

Fixed by #7008