Dragging - Fix unintended Cargo dependency and improve ragdoll/disconnection handling

[johnb432]

When merged this pull request will:

• The improvement part of Dragging - Corpse carrying and dragging - continued #9269, plus a third one (last in the list below).

1. Makes ace_dragging depend on ace_cargo. There are functions and stringtable entries from ace_cargo that are called, see here, here and here. If ace_dragging isn't supposed to be dependent on ace_cargo, then ace_dragging will need to be adjusted accordingly.
2. Disconnection detection for units carrying or dragging was done previously with the HandleDisconnect mission EH. In my testing (self-hosted MP) HandleDisconnect fires too late and when trying to read the QGVAR(isCarrying)/QGVAR(isDragging) variables, it just returns false, regardless if a unit if carrying/dragging something or not. This makes it impossible for carried/dragged objects to be dropped properly.
   PlayerDisconnected fires before and therefore makes it possible to drop carried/dragged objects correctly. However, I'm unsure if there are any disadvantages to PlayerDisconnected.
3. Added a check to FUNC(canDrag) and FUNC(canCarry), where it disables dragging/carrying if a unit is in ragdoll animation. This is to prevent odd behaviour. As it is now, you can try to drag a unit in ragdoll, but they stay in place while you go into the drag animation.

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[LinkIsGrim]

If ace_dragging isn't supposed to be dependent on ace_cargo, then ace_dragging will need to be adjusted accordingly.

This wasn't the case until recently. Should be adjusted using conditions. Rest is fine.

[johnb432]

Nice adjustments and additions @LinkIsGrim !