When we submit a task to a thread pool for asynchronous execution, we
are returned a future. Since we submitted to go asynchronous, these
futures are not inspected for failure (we would have to block a thread
to do that). While we have on failure handlers for exceptions that are
thrown during execution, we do not handle throwables that are not
exceptions and these end up silently lost. This commit adds a check
after the runnable returns that inspects the status of the future. If an
unhandled throwable occurred during execution, this throwable is
propogated out where it will land in the uncaught exception handler.
Relates #28667
3e846ab251