Fixed the RTL return path error for multi-axis models when RTL_TYPE is 1

[DrinkingHook]

Issue Description

Problem Summary
In multi-axis vehicles with RTL_TYPE set to 1 (mission land on RTL), the RTL behavior during mid-mission return incorrectly prioritizes landing at the mission_land waypoint, even if the home position is closer. This results in the vehicle flying directly to mission_land for landing, potentially leading to inefficient or unsafe paths.

Question
Since I am a beginner, I don't know if this is the original design. If so, I'm sorry to bother you.

1. If this is a specific mode and mission_land exists, then all models will fly directly to mission_land after triggering return. However, the VEHICLE_TYPE_ROTARY_WING model of VTOL does not follow this design, but because it is almost similar to multi-axis, I submitted this PR.

Expected Behavior
The RTL logic should evaluate the distance to both the home position and mission_land, then select the closer one for landing—similar to the gz_standard_vto model in Gazebo simulation. Fixed-wing models should continue to land at mission_land as per current design.

Reproduction Steps

1. Configure a multi-axis vehicle model in PX4 SITL or hardware setup.
2. Set RTL_TYPE to 1.
3. Start a mission with a defined mission_land waypoint farther from home.
4. Trigger RTL mid-mission
5. Observe the vehicle path: It flies straight to mission_land regardless of proximity to home.

Testing

• Verified in SITL with gz_standard_vto and 'gz_x500'
• Confirmed fixed-wing behavior unchanged.
• Edge cases tested: RTL near home vs. far from both points.

Screenshot

1. before the change

2. adjusted