Update submodule mavlink to latest Fri May 19 12:38:47 UTC 2023

    - mavlink in PX4/Firmware (0ff9816): mavlink/mavlink@3ee5382
    - mavlink current upstream: mavlink/mavlink@18955a0
    - Changes: mavlink/mavlink@3ee5382...18955a0

    18955a04 2023-05-11 Nick Exton - common.xml: Add MAV_RESULT_COMMAND_LONG_ONLY and MAV_RESULT_COMMAND_INT_ONLY to MAV_RESULT (#1982)
b92321ba 2023-03-30 Hamish Willee - Update message_definitions/v1.0/common.xml
58ff70f4 2023-03-30 Hamish Willee - COMMAND_ACK progress/result_param2 clarification
31b4aebb 2023-05-11 Julian Oes - cmake: locally install pip dependencies (#1984)
e9bf6a61 2023-05-10 Hamish Willee - Gimbal manager messages - remove WIP tagging (#1980)
0416967f 2023-05-10 Beat Küng - development: changes to standard flight modes (#1915)
ce00667f 2023-05-04 Jonas Vautherin - New cmakelists (#1977)
fdef5cc0 2023-05-03 Nick Exton - common.xml: Prefer COMMAND_INT when command includes altitude field (#1983)
89676d1d 2023-05-03 Nick Exton - common.xml: Add ZOOM_TYPE_HORIZONTAL_FOV to CAMERA_ZOOM_TYPE enum (#1979)