Add support for Immutables

Example:

// User.java
import org.immutables.value.Value;

@Value.Immutable
public interface User {
    @Value.Default
    default String getName() {
        return NameGenerator.random();
    }
}

// ImmutableUser.java
import org.immutables.value.Generated;

@Generated(from = "User", generator = "Immutables")
@SuppressWarnings({"all"})
@javax.annotation.processing.Generated("org.immutables.processor.ProxyProcessor")
public final class ImmutableUser implements User {
  private final String name;

  private ImmutableUser(ImmutableUser.Builder builder) { // What if we ignore this?
    this.name = builder.name != null
        ? builder.name
        : Objects.requireNonNull(User.super.getName(), "name");
  }

  private ImmutableUser(String name) { // Should use this
    this.name = name;
  }

  // ...

  @Generated(from = "User", generator = "Immutables")
  public static final class Builder {
    // ...
  }
}

In this code, it can't find constructor because there is a constructor that uses Builder as a parameter.

I don't want something big like creating constructor using Builder. If the class is auto-generated and the constructor parameter is builder, I want it to ignore it.

I could add @Value.Style(privateNoargConstructor = true) annotation to interface, so there would be noArg constructor but that's just workaround. It's not working with transiant types, etc. I prefer first solution if it's okay.

Start with src/main/java/org/springframework/data/mapping/model/PreferredConstructorDiscoverer.java around line 112, where constructor discovery fails for the generated Immutables class. Compare the builder-parameter constructor with the direct String constructor and define completion as ignoring the generated builder constructor without creating a constructor from Builder.