Callback in Passenger during UnloadCargo before re-adding it to the world

[michaeldgg2]

This PR adds extension point in Passenger, which is used byUnloadCargo. The callback is called just before adding the Passenger actor back to the world and by default cancels actor's activities (which keeps the original behavior intact).

On the other hand by preserving actor's queued activities, new useful scenarios such as "ride and capture" attacks open up:

• queue loading engineers (or other capture-capable actors) onto a transporter (Cargo actor)
• also queue the capture order for the engineers of the target building (or other capturable actor)
• queue moving the transporter next to target building and queue deploy order

Example usage in OpenE2140 mod (here, any infantry actor can capture buildings):

This PR also fixes bug, when passenger actor's activities were not canceled, when it was ejected after the Cargo actor was destroyed.

The PR supersedes #21079.

[michaeldgg2]

This is GIF of the bug demonstrated in TS:

[PunkPun]

Virtualisation doesn't hurt here