Resolves: #11069

After checking the behaviour, it seems to me that we don't need to
capture any Boom responses, as the errors that may cause a `5xx`
response are already captured by the core logic. To add an option to
control this behaviour, we need to update the usage of
`hapiErrorPlugin`, converting it to a function signature, which IMO may
not worth doing, as I'm not sure if users in general would need to use
it.

This also adds `expectError()` to the `node-integration-tests` runner to
allow `5xx` responses to be tested.