Merge mavlink failsafe mode decoding

[RomanLut]

It is better to show nothing instead of incorrect information.

1) Under failsafe state, INAV sends customMode = PLANE_MODE_ENUM_END / COPTER_MODE_ENUM_END. Currently it is not handled at all, showing "Armed | Acro | Failsafe", which is not true. It is better to show just "Armed | Failsafe" untill correct mode is available ( F.e. "Armed | RTH | Failsafe" ).

2) INAV sends custom mode = AUTO for Mission and for Landing. It is possible to distinguish between Mission and Landing inspecting MAV_STATE_CRITICAL flag. BUT it seems that qczek LRS is modifying mavlink messages and sets MAV_STATE_CRITICAL flag, which causes last mode (Mission) to be decoded as Landing. This is bad experience for the user, it is better to show nothing for the case customMode = AUTO & Failsafe because it is not possible to realibly distingush correct mode.

[sonarcloud[bot]]

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