Fix multiple rebel squad/vehicle price bugs

[jaj22]

What type of PR is this.

1. Bug
2. Change
3. Enhancement

What have you changed and why?

Both constructed and single-vehicle AA trucks were being underpriced on purchase due to not calculating truck + static AA costs as the other code did. This PR fixes this for both cases with a horrible hack.

Edit: Additional vehicle price bugs fixed:

• Fixed doubled check price for AA and AT vehicles (missing isInfantry check).
• Fixed AT car check price adding SDKTruck price.
• Fixed ancient bug where zu-23 rebel AA trucks were not refunded on dismissal.
• Fixed bug where vanilla AA trucks were double-refunded.
• Fixed misleading error message when you didn't have enough money to purchase a transport vehicle.
• Fixed wrong price shown for transport vehicle.
• Fixed squad mortars and MGs not being charged for.

Please specify which Issue this PR Resolves.

closes #2150
closes #2152

Please verify the following and ensure all checks are completed.

1. Have you loaded the mission in LAN host?
2. Have you loaded the mission on a dedicated server?

Is further testing or are further changes required?

1. No
2. Yes (Please provide further detail below.)

[HakonRydland]

one small change and a clerification

[jaj22]

Changed to only attempt attached-vehicle refunds if they're in vehFIA. Anything else is left alone (or dumped on the ground, if the parent object is deleted).