Fix and jsonize item dropping and trap conversion in trap-vehicle interaction

[Qrox]

Summary

SUMMARY: Bugfixes "Fix bugs in trap-vehicle interaction"

Purpose of change

1. Fix some traps (such as bear traps) duplicating when run over by vehicles.
2. Fix known traps forgotten after being run over and converted to other traps (such as tr_shotgun_2 converted to tr_shotgun_1).
3. Make traps known to the player if seen in action during trap-vehicle interaction.
4. Fix double-barrel shotgun trap turning into single-barrel shotgun trap when run over by vehicles.
5. Vehicles now trigger traps when running into them, instead of running off, to be consistent with player-trap interaction.
6. Jsonize item dropping and trap conversion in trap-vehicle interaction.

Describe the solution

1 is fixed with json modification.
4 is fixed by adding a new "tr_shotgun_2_1" trap type as the half-fired double-barrel shotgun trap.
5 is fixed by handling trap-vehicle interaction after moving vehicles.

Additional context

There are some inconsistencies between trap-vehicle interaction and player-trap interaction (such as those of shotgun traps), but that's out of the reach of this PR.