Default Connect Router/Resolver/Splitter

### Feature Description

Currently, Configuration Entries are associated to precise services using the "name" attribute".
It could be interesting to create router/resolver/splitter that apply on all services, without depending from the service name.

#### Use Case(s)

In our case, we are assigning blue/green service instance using service meta and redirecting blue/green traffic according a HTTP header. This could be applied to every service in the cluster but we have to create a config entry for every service.

Tell me if it was already asked (but I did not found).
Yours faithfully