[Feature] Modifier for GM screen right-click to order movement of multiple AI ships toward specific coordinates

Issue

When right-clicking a vacant space on the GM screen radar while selecting multiple AIController entities, the entities should receive orders to move toward the cursor's coordinates. Instead, they all receive orders to move at an angle and to a distance relative to the center coordinates of the selection. This results in most of the selected ships not moving toward the intended coordinates, either selecting vectors far from the coordinates or not moving at all if right-clicking the center of the selection.

This doesn't affect right-click orders when selecting a single ship, or when selecting multiple ships and right-clicking an entity to issue attack/defend orders. In both cases the expected behavior (moving to the clicked coordinates) occurs.

Steps to reproduce

1. Open GM screen on a running scenario with multiple AIController entities present
2. Select multiple AIController entities
3. Right-click on empty space

Expected behavior

All ships receive orders to move toward the same coordinates, at the right-clicked point of the map.

Observed behavior

Ships receive orders to move on a vector with an angle and distance that appears to be relative to the centroid of the selected ships.

https://github.com/user-attachments/assets/68274f43-be3f-406e-a3d8-92f64b6c5f46

Reproduce this on the GM screen radar with multiple AIController entities, selecting empty space and right-clicking. Trace the GM screen right-click movement-order entry point and compare it with single-ship orders and multi-ship attack/defend orders. Done means all selected ships receive movement orders toward the clicked map coordinates rather than vectors relative to their selection centroid.