Clean up javax.inject annotations in restconf-nb

The only thing ODLMICRO-24 can reasonably want now is that restconf-nb provides correct @Singleton annotations. This depends on NETCONF-959, which will clean up the lifecycle enough for this to be feasible.

At the end of the day, Guice does not really deal with configuration injection of which restconf-nb has plenty. It also has a ton of invalid Singletons, as it really should only be wired through JaxRsNortbound.

Add @Singleton annotation to it an provide an @Inject constructor, which will just take default values. Also remove any other @Singletons we end up overriding – for example RestconfApplication, which just cannot work (because of StreamsConfiguration).