Add ServerBuilder.coroutinService as Kotlin extension method

[minwoox]

CoroutineHttpService was introduced in #5603.
However, adding the service to a ServerBuilder using lambda requires an explicit type declaration, which can be cumbersome for users.
If we provide the coroutineService method, users will easily add a CoroutineHttpService using lambda.

Server
  .builder()
  .coroutineService("/path", myCoroutineService)
  ...