Allow Rabbit Streams binding to use Kotlin lambdas

Not sure if it worth separate ticket, but when trying to use Kotlin functional binder for GCP pub/sub Spring is logging the is not eligible for getting processed by all BeanPostProcessors message for an Autowired class on a start up (the app still starts).

It is not logging this message when using Consumer interface;

Example with Kotlin lambdas which causes the INFO message:

....
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration

@Configuration
class TicketSink(@Autowired private val ticketService: TicketService) {

    @Bean
    fun processTicketMsg(): (Ticket) -> Unit = { ticketService.saveTicket(it) }
}

This way there are many messages including the TicketService

INFO 21704 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'ticketService' of type 
[service.TicketService] is not eligible for getting processed by all BeanPostProcessors 
(for example: not eligible for auto-proxying)

All the other classes that are dependencies in the TicketService are also logged with the same message

Example with Consumer interface where there is no TicketService related messages:

import org.springframework.beans.factory.annotation.Autowired
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import java.util.function.Consumer

@Configuration
class TicketSink(@Autowired private val ticketService: TicketService) {

    @Bean
    fun processTicketMsg() = Consumer<Ticket> { ticketService.saveTicket(it) }
}

This way there is a set of the messages that mention some internal classes only, like

Bean 'org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration' of type 
[org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration] is not eligible for getting processed by all 
BeanPostProcessors (for example: not eligible for auto-proxying)

spring-cloud / spring-cloud-stream

Allow Rabbit Streams binding to use Kotlin lambdas #1935