Fix onClientVehicleDamage firing twice for explosions

[QueryOfficial]

Summary

Stop onClientVehicleDamage from firing twice for a single explosion hit, and correct the event arguments that San Andreas reports incorrectly for explosion damage.

• Suppress the duplicate VehicleDamage event after InflictDamage has already emitted onClientVehicleDamage, while still honouring cancelEvent on follow-up damage application.
• Record the last explosion position/weapon/creator in CClientExplosionManager.
• In VehicleDamageHandler, remap WEAPONTYPE_EXPLOSION (51) and (0,0,0) damage position to the real causative weapon and blast origin (same approach as ped explosion damage).

Motivation

Fixes #5068.

A single RPG/grenade hit was producing two onClientVehicleDamage callbacks: one from CVehicle::InflictDamage (real loss, weapon 51, position (0,0,0)) and another from the subsequent VehicleDamage call (often loss = 0, with a usable position). Scripts could not reliably use the event for explosion damage.

Test plan

1. Spawn a vehicle and attach a debug handler to onClientVehicleDamage that prints attacker, weapon, loss, and x/y/z.
2. Hit the vehicle once with an RPG: confirm a single event, weapon is rocket (not 51), position is near the blast (not (0,0,0)), and loss is non-zero.
3. Repeat with a grenade: same expectations with grenade weapon id.
4. Cancel the event in the handler and confirm vehicle health is not reduced for that hit.
5. Sanity-check normal collision damage still fires onClientVehicleDamage once with expected args.
6. Sanity-check bullet/tyre damage paths still behave as before.

Checklist

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