Fix jetpack behavior

[FileEX]

Summary

In GTA, when you equip a jetpack, the weapon is automatically switched to a pistol, tec-9, or uzi if you have one of these weapons. Otherwise, the weapon is hidden from the player’s hands, but the slot remains unchanged, which causes two issues:

• Issue Texture bug with setJetpackWeaponEnabled #508, where weapons are invisible
• The state described in PR Fix #3659 weapon switching (scroll and Q+E) while using Jetpack  #3573 - if you pick up a jetpack while holding a e.g chainsaw/molotov, the weapon model disappears, but the weapon sound and its HUD icon remain

In GTA, when you remove the jetpack, the slot is restored to the one you had before equipping it. For example, if you are holding an AK-47, then equip a jetpack and it switches to an uzi, after removing the jetpack you get the AK-47 back. PR #3573 changed this behavior so that after removing the jetpack, the slot is always reset to 0.

From the GTA code, it appears that Rockstar also intended to include the sawed-off shotgun for jetpack use, but a trivial mistake prevented it from working.

			// this is to let the player use other 1 handed weapons when flying a jetpack!
			else if(nVehicleType==1 && m_WeaponSlots[WEAPONSLOT_TYPE_SHOTGUN].m_eWeaponType==WEAPONTYPE_SAWNOFF_SHOTGUN
			&& m_WeaponSlots[WEAPONSLOT_TYPE_SHOTGUN].m_nAmmoTotal>0)
			{
				nDoDrivebySlot = WEAPONSLOT_TYPE_HANDGUN;
			}
			else if(nVehicleType==1 && m_WeaponSlots[WEAPONSLOT_TYPE_HANDGUN].m_eWeaponType==WEAPONTYPE_PISTOL
			&& m_WeaponSlots[WEAPONSLOT_TYPE_HANDGUN].m_nAmmoTotal>0)
			{
				nDoDrivebySlot = WEAPONSLOT_TYPE_HANDGUN;
			}

This PR resolves the issues described above.

Motivation

#3510 (comment)

Test plan

See issues: #508, #3659

1. Get chainsaw
2. Get jetpack
3. Remove jetpack
4. The slot should be reset to the chainsaw, but it is instead reset to 0.

TL;DR

• Removing the jetpack restores the previous slot, exactly like in GTA:SA
• While using a jetpack, you can now also use the sawed-off shotgun in addition to pistol, Uzi, and Tec-9

Checklist

• Your code should follow the coding guidelines.
• Smaller pull requests are easier to review. If your pull request is beefy, your pull request should be reviewable commit-by-commit.

[Lpsd]

The proposed solution in #3510 (comment) sounds good - how come this wasn't implemented?

[FileEX]

The proposed solution in #3510 (comment) sounds good - how come this wasn't implemented?

Due to the ongoing feature freeze, I want to do this in a separate PR so that the bugfix one doesn’t sit indefinitely just because it adds a new feature.