[storage] Put Storage Impls Behind Actor Interface

[patrick-ogrady]

To avoid blocking in actor loops on storage, we should create actor interfaces that send messages back with storage results.

This should greatly improve performance on slow disks (that would otherwise improve our message handling rate).

[patrick-ogrady]

Instead of replying to the actor that requested data, they could instead be provided a oneshot to respond to the caller from storage.

For "puts", we may still want to get a message back.