Add NPC_GetVehiclePos and NPC_GetVehicleRot natives

[Revelts]

Closes #1197.

Summary

Adds the getter counterparts to NPC_SetVehiclePos / NPC_SetVehicleRot, as requested in #1197.

• INPC::getVehiclePosition() and INPC::getVehicleRotation() — SDK side (see paired SDK PR add get vehicle position and rotation open.mp-sdk#71)
• NPC::getVehiclePosition() / NPC::getVehicleRotation() — implementations in Server/Components/NPCs/NPC/npc.cpp
• NPC_GetVehiclePos(npcid, &Float:x, &Float:y, &Float:z) and NPC_GetVehicleRot(npcid, &Float:x, &Float:y, &Float:z) — PAWN natives in Server/Components/Pawn/Scripting/NPC/Natives.cpp

Both getters return zero/identity when the NPC is not currently in a vehicle, matching the silent no-op semantics of the existing setters.

Depends on

• add get vehicle position and rotation open.mp-sdk#71 — must merge first. Submodule pointer in this PR points to the head of that branch (324eb80); it will need to be re-pointed to the merged SHA once the SDK PR lands.

A companion PR to openmultiplayer/omp-stdlib for the .inc declarations of NPC_GetVehiclePos / NPC_GetVehicleRot is still to be opened.

Test plan

• CI build green (Linux/Windows/macOS) once SDK PR merged and submodule re-pointed
• In-game: spawn NPC, put in vehicle, confirm NPC_GetVehiclePos and NPC_GetVehicleRot return values matching what was written via the corresponding setters
• Out of vehicle: confirm both natives return zeroed Vector3