Embedded `RemoteActorError`s and other exceptions

[goodboy]

Relates heavily to #5.

After doing a lot of involved messaging / runtime reworking in #261 I've realized it would sure be a lot more friendly to support embedded / nested RemoteActor errors.

Here's a simple example: root spawns child, child starts task in root and that task errors making the error flow look like:

root --RemoteActorError[Exception] --> child root <--RemoteActorError[RemoteActorError[Exception]]] -- child

The problem is that currently there's no way to dig out the original Exception details from the nested rme. How could we offer this such that, for example, a task can introspect and understand more complex error flows?

Questions:

• Is this over the top and we should try to keep things flat instead of nested (python zen stuff)?
• where should nesting end? In theory you could have a ping pong nesting of a single error under the right conditions in which case does something like the messaging equivalent of a RecursionError make sense?
• what actual source exception details / metadata should we be serializing (would love to keep it super simple and with cross-lang support in mind), which is basically the main question #5?

Resources:

• raise from syntax is one built-in way we can chain exception data (see this SO) but how would we get the nested form of this? A custom tb serializer?