DerivedActorRef::send_after function always returns InvalidActorType

[utdemir]

Describe the bug

DerivedActorRef::send_after function always return an InvalidActorType which is unexpected given the typed interface.

Looking at the source a bit - it appears to me that they simply get the cell from the reference and call the send_after function with it, disregarding the converter that needs to be applied.

To Reproduce

I opened a draft PR with an updated test case that reproduces it: #378

But essentially:

• Have a DerivedActorRef with a From instance that is not identity.
• Call derived_ref.send_after(some_duration, some_message)
• Observe the message not being sent & the result of the send being Err(InvalidActorType)

Expected behavior

I would expect the send_after and send_interval functions to work on DerivedActorRef the same as ActorRef.