Use position predicate for PlayerMessage

When using Message object in order to deliver a message in a particular position we usually have to do the next

```
createMessage(target)
?.setLooper(Looper.getMainLooper())
?.setPosition( /* mediaItemIndex= */mediaItemIndex, /* positionMs= */positionInMs)
?.setPayload(playbackMessage)
?.setDeleteAfterDelivery(false)
?.send()
```

Problem is that in some cases we want to deliver the message given a condition for example.

When mPlayer.currentPosition >= positionInMs , so if the user is seeking beyond this positionInMs, the message should be delivered.

Actually we can not set a predicate that meet a particular condition when delivering a message forcing us to add extra code to cover other conditions.

### Propose
Allow to add a predicate when creating the message: predicate: (T) -> Boolean, so the message should be delivered when the predicate is true.