\Exception doesn't work as a catch-all because not everything extends
\Exception. For example, there was a problem where the messaging worker
didn't catch an exception here:
} catch (\Exception $e) {
$deliveryErrors[] = 'Failed sending to targets ' . $batchIndex + 1 . '-' . \count($batch) . ' with error: ' . $e->getMessage();
} finally {
As such, $deliveryErrors stayed as an empty array. In this case, the
$adapter->send() threw a TypeError which extends Error which implements
Throwable. Updating the catch to catch \Throwable ensures the error is
caught and $deliveryErrors gets updated.
