JIRA: https://jira.spring.io/browse/INT-4421
If a component invoked by an SPCA threw a `MessagingException` with no
`failedMessage`, the resulting ErrorMessage payload had no `failedMessage`.
The `UnicastingDispatcher` had a check for this so it wasn't an issue
as long as at least one `DirectChannel` was between the poller and the
component.
Promote the wrapping code to `IntgrationUtils` and invoke it from
places that blindly rethrew `MessagingException`s.
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