MAV_TYPE_VTOL_DUOROTOR renamed in current MAVLink

This might not affect ArduPilot (yet) but `MAV_TYPE_VTOL_DUOROTOR` was renamed to [MAV_TYPE_VTOL_TAILSITTER_DUOROTOR](https://mavlink.io/en/messages/common.html#MAV_TYPE_VTOL_TAILSITTER_DUOROTOR).
When this changes it will probably break at this line: https://github.com/ArduPilot/MAVProxy/blob/master/MAVProxy/modules/mavproxy_link.py#L744

Some context. I am trying to use MAVProxy to test custom messages in PX4. So I install MAVProxy, uninstall Pymavlink, clone mavlink/mavlink and then rebuild the pymavlink using setup.py. This is a pretty good trick because rebuilding pymavlink is very easy, and all you need to do to add a new dialect so you can check a message is being sent is to copy the XML into the mavlink repo dialects folder.

This all works, and MAVProxy connects, but then I get an error as shown below::

```
LOITER> Mode LOITER
Exception in thread main_loop:
Traceback (most recent call last):
File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
self.run()
File "/usr/lib/python3.10/threading.py", line 953, in run
self._target(*self._args, **self._kwargs)
File "/home/ubuntu/.local/bin/mavproxy.py", line 1155, in main_loop
process_master(master)
File "/home/ubuntu/.local/bin/mavproxy.py", line 842, in process_master
msgs = m.mav.parse_buffer(s)
File "/usr/local/lib/python3.10/dist-packages/pymavlink-2.4.41-py3.10.egg/pymavlink/dialects/v20/ardupilotmega.py", line 21911, in parse_buffer
m = self.parse_char(s)
File "/usr/local/lib/python3.10/dist-packages/pymavlink-2.4.41-py3.10.egg/pymavlink/dialects/v20/ardupilotmega.py", line 21850, in parse_char
self.__callbacks(m)
File "/usr/local/lib/python3.10/dist-packages/pymavlink-2.4.41-py3.10.egg/pymavlink/dialects/v20/ardupilotmega.py", line 21838, in __callbacks
self.callback(msg, *self.callback_args, **self.callback_kwargs)
File "/home/ubuntu/.local/lib/python3.10/site-packages/MAVProxy/modules/mavproxy_link.py", line 1008, in master_callback
self.master_msg_handling(m, master)
File "/home/ubuntu/.local/lib/python3.10/site-packages/MAVProxy/modules/mavproxy_link.py", line 731, in master_msg_handling
mavutil.mavlink.MAV_TYPE_VTOL_DUOROTOR,
AttributeError: module 'pymavlink.dialects.v20.ardupilotmega' has no attribute 'MAV_TYPE_VTOL_DUOROTOR'
Exception in thread log_writer:
Traceback (most recent call last):
File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
^CFatal Python error: _enter_buffered_busy: could not acquire lock for at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=0x0000563640a44420)
```

Start in MAVProxy/modules/mavproxy_link.py around the MAV_TYPE_VTOL_DUOROTOR reference in master_msg_handling. Compare that reference with the current MAVLink name shown in the issue and verify behavior using the reported pymavlink setup. Done means MAVProxy no longer raises the AttributeError when processing the message.

Written by the indexing model from the issue text.