Descriptive CLI Error Messages

The arguments -X, -H, -u, and -p are all currently required to successfully run amqpfind. As it stands now, when a user doesn't specify one of the previous options, amqpfind will spit out a cryptic error message:

  ...
  File "/Users/mdrexler/.venv/lib/python3.12/site-packages/pika/adapters/blocking_connection.py", line 451, in _create_connection
    raise self._reap_last_connection_workflow_error(error)
  File "/Users/mdrexler/.venv/lib/python3.12/site-packages/pika/connection.py", line 1855, in _on_connection_start
    self._send_connection_start_ok(*self._get_credentials(method_frame))
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mdrexler/.venv/lib/python3.12/site-packages/pika/connection.py", line 1643, in _get_credentials
    response) = self.params.credentials.response_for(method_frame.method)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mdrexler/.venv/lib/python3.12/site-packages/pika/credentials.py", line 79, in response_for
    b'\0' + as_bytes(self.username) + b'\0' + as_bytes(self.password))
            ^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mdrexler/.venv/lib/python3.12/site-packages/pika/compat.py", line 186, in as_bytes
    return value.encode('UTF-8')
           ^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'encode'

It would be nice to improve the error messages when one of the flags are missing so users know why their amqpfind command isn't working.