Fix aim pose desync when a weapon is given while the aim/fire button is held

[TheCrazy17]

Summary

CNetAPI::WritePlayerPuresync now clears the aim/fire (RightShoulder1/ButtonCircle) keysync bits in the outgoing on-foot puresync packet when the local ped's secondary attack task isn't actually TASK_SIMPLE_USE_GUN, instead of blindly forwarding the raw button state.

Motivation

Fixes #518, an ancient bug open since 2018.

GTA:SA only starts TASK_SIMPLE_USE_GUN on a fresh button press, not while held. If a weapon is given while aim is already held from before, the local pose looks right but the puresync protocol has no explicit "is aiming" wire bit - every reader rederives it from the raw keysync bits, which were still "held", so everyone else saw the player stuck aiming/running-aiming.

Before

Test plan

Reproduced locally with two clients:

• Held aim with no weapon, then ran giveWeapon(player, 34, 30, true) (sniper) via a server-side bindKey test script while still holding aim.
• Before the fix: the local client correctly showed no aim pose, but the second client watching remotely saw the player aiming and running in the aiming animation.
• After the fix: both clients show the same (correct, non-aiming) pose.
• Also confirmed the fix covers picking up a weapon from a ground pickup, since CPickup.cpp calls the same CStaticFunctionDefinitions::GiveWeapon path used by the scripted function.

Checklist

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