Remove a unary method which gets overloaded by a varargs method

[ikhoon]

Some APIs in Armeria provide both a unary method and a varargs method. (e.g. ServerListenerBuilder)

armeria/core/src/main/java/com/linecorp/armeria/server/ServerListenerBuilder.java

Lines 171 to 182 in e872d75

	public ServerListenerBuilder whenStarted(Consumer<? super Server> consumer) {
	serverStartedCallbacks.add(requireNonNull(consumer, "consumer"));
	return this;
	}
	/**
	* Adds {@link Consumer}s invoked when the {@link Server} is started.
	*
	* @see ServerListener#serverStarted(Server)
	*/
	@SafeVarargs
	public final ServerListenerBuilder whenStarted(Consumer<? super Server>... consumers) {

That is a good pattern to avoid creating an additional single-sized array for a single parameter. However, some JVM languages such as Scala 2.12 cannot properly infer the input type when a lambda expression is used.
For example:

ServerListener.builder()
              // failed to compile with 'missing parameter type'
              .whenStarted { server => ... } 
              .build()

If we remove whenStarted(Consumer<? super Server> consumer) from the overloaded methods, the compiler correctly infers the type parameter for the lambda expression.
whenStarted() rarely called in an application life cycle, so the overhead is almost zero.
And we can apply this approach to other non-frequently called methods.

As this is breaking changes, this issue could be resolved when Armeria 2.0 is released.

[ikhoon]

I saw a build error on another ambiguous reference:

ambiguous reference to overloaded definition,
both method annotatedService in class ServerBuilder of type (service: Any, exceptionHandlersAndConverters: Object*)com.linecorp.armeria.server.ServerBuilder
and  method annotatedService in class ServerBuilder of type (service: Any)com.linecorp.armeria.server.ServerBuilder

with

armeria/core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java

Lines 1021 to 1037 in 2790d65

	public ServerBuilder annotatedService(Object service) {
	return annotatedService("/", service, Function.identity(), ImmutableList.of());
	}
	/**
	* Binds the specified annotated service object under the path prefix {@code "/"}.
	*
	* @param exceptionHandlersAndConverters the {@link ExceptionHandlerFunction}s,
	* the {@link RequestConverterFunction}s and/or
	* the {@link ResponseConverterFunction}s
	*/
	public ServerBuilder annotatedService(Object service,
	Object... exceptionHandlersAndConverters) {
	return annotatedService("/", service, Function.identity(),
	ImmutableList.copyOf(requireNonNull(exceptionHandlersAndConverters,
	"exceptionHandlersAndConverters")));
	}

[ikhoon]

 overloaded method service with alternatives:
  (serviceWithRoutes: com.linecorp.armeria.server.HttpServiceWithRoutes,decorators: java.util.function.Function[_ >: com.linecorp.armeria.server.HttpService, _ <: com.linecorp.armeria.server.HttpService]*)com.linecorp.armeria.server.ServerBuilder <and>
  (serviceWithRoutes: com.linecorp.armeria.server.HttpServiceWithRoutes,decorators: Iterable[_ <: java.util.function.Function[_ >: com.linecorp.armeria.server.HttpService, _ <: com.linecorp.armeria.server.HttpService]])com.linecorp.armeria.server.ServerBuilder <and>
  (route: com.linecorp.armeria.server.Route,service: com.linecorp.armeria.server.HttpService)com.linecorp.armeria.server.ServerBuilder <and>
  (pathPattern: String,service: com.linecorp.armeria.server.HttpService)com.linecorp.armeria.server.ServerBuilder

with

armeria/core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java

Lines 1070 to 1074 in f52f9d0

	public final ServerBuilder service(
	HttpServiceWithRoutes serviceWithRoutes,
	Function<? super HttpService, ? extends HttpService>... decorators) {
	return service(serviceWithRoutes, ImmutableList.copyOf(requireNonNull(decorators, "decorators")));
	}