Motivation:
Users cannot inject an instance, which has constructor parameters, through `@Decorator` and other annotations.
It would be nice if we provide a way to inject dependencies.

Modifications:
- Add `DependencyInjector` to inject the instances that are specified in an annotated service.
  - If a `DependencyInjector` is not set, `ReflectiveDependencyInjector` is used to keep the backward-compatibility
  - If a `DependencyInjector` is set, `BuiltInDependencyInjector` is applied at first to support built-in classes.
- Add `SpringDependencyInjector` that injects using `BeanFactory`. 
  - You can set `armeria.enable-auto-injection` to `true` to apply `SpringDependencyInjector`.
  - You can also create a bean for `DependencyInjector`.

Result:
- Close #4006
- You can now inject dependencies using `DependencyInjector` to annotated services.
  ```java
  // Inject authClient that is needed to create the AuthDecorator.
  WebClient authClient = ...
  DependencyInjector injector = DependencyInjector.ofSingletons(new AuthDecorator(authClient));
  serverBuilder.dependencyInjector(dependencyInjector, true);

  // An annotated service that uses AuthDecorator.
  @get("/foo")
  @decorator(AuthDecorator.class)
  public FooResponse foo(FooRequest req) {
      // Authrorized request.
      ...
  }
  
  // authClient is injected.
  class AuthDecorator implements DecoratingHttpServiceFunction {
      AuthDecorator(WebClient authClient) { ... }

      @OverRide
      public HttpResponse serve(HttpService delegate, ServiceRequestContext ctx, HttpRequest req)
              throws Exception {
          // Authorize the request.
          ...
      }
  }
  ```