Motivation:

- Related issue: line#5382
- It'd be nice if a user can access the information provided by
`AnnotatredService`, but it is not part of the public API.

### Modifications:

- Split `AnnotatedService` into `AnnotatedService` (interface) and 
  `DefaultAnnotatedService` (implementation).

### Result:
- Closes line#5382

Before:
```java
        ServiceRequestContext serviceRequestContext = ServiceRequestContext.current();
        AnnotatedService service = serviceRequestContext.config().service().as(AnnotatedService.class);

        // This doesn't compile.
        // service.method(); 
        // service.defaultStatus();
```

After:
```java
        ServiceRequestContext serviceRequestContext = ServiceRequestContext.current();
        AnnotatedService service = serviceRequestContext.config().service().as(AnnotatedService.class);

        // This compiles and provides useful properties.
        service.method(); 
        service.defaultStatus();
```

---------

Co-authored-by: Ikhun Um <[email protected]>
Co-authored-by: Trustin Lee <[email protected]>
Co-authored-by: jrhee17 <[email protected]>
Co-authored-by: minux <[email protected]>