Make acknowledgement required in IbcReceiveResponse::new

[webmaster128]

Creating an IbcReceiveResponse without acknowledgement leads to

failed to execute message; message index: 0: acknowledgement cannot be empty: invalid acknowledgement: invalid request

which makes sense. We should change this pattern:

-    Ok(IbcReceiveResponse::new()
-       .set_ack(ack)
+    Ok(IbcReceiveResponse::new(ack)
         .add_attribute("action", "acknowledge_ibc_query")
         .add_attribute("job_id", job_id)
         .add_submessage(msg))

[webmaster128]

As discussed with @chipshort. Let's keep the optionality separate (implemented in #1892) as this might be a bigger issue. Here we just add the acknowledgement to the IbcReceiveResponse constructor and remove set_ack.