capsules/core/console: add asynchronous error reporting facility

[lschuermann]

Imported from @ppannuto's comment on #3585:

As-is, this drops errors silently :(. But, we're hamstrung by the interface of the stabilized console driver here, which didn't have any way to report asynchronous errors on the write path.

I feel like we should deprecate upcall 1 and add an upcall 3 or something.

This is simple and clean enough that this might be the right problem to explore how we want to manage sustaining deprecated-and-future APIs in-tree. We punted on that problem once already with the LEDs, but this is going to keep coming up, and we need to develop some principled approaches.

Originally posted by @ppannuto in #3585 (review)

Marking as release-blocker, such that we triage this prior to the next breaking release.