Unbuffered Channels in ChannelBasedReceiverRegistry

The channels are created without buffers:

```go
ch := make(chan kube.EnhancedEvent)
``` 

When events come in rapidly, the goroutine at line 31 tries to send to the channel, but if the receiver goroutine is blocked (e.g., on a slow sink), this can cause goroutine buildup and eventually hang.
