Propagate 'EINTR' errnos as distinct errors to the user instead of hiding them in a generic 'InternalError' #1556

Brief feature description

While EINTR errnos are propagated as Interrupted or InterruptedBySignal error up in the stack, at some point they are converted to a generic InternalError.

In order to give the user a chance to react on this error, it needs to be communicated by a distinct error code like InterruptedBySignal up in the stack.