Custom, crew-buildable vendors

[FunnyMan3595]

What Does This PR Do

Adds the ability for vendors to hold actual items (rather than just typepaths), and uses it to implement a custom vendor type, which is available in the vending board and as a kit in the bar and kitchen vendors.
Migrates /obj/machinery/economy to the new attack chain.

Why It's Good For The Game

Custom vendors are not only fun for admin use, they allow chefs, cooks, and other folks with stuff to sell to do it in a standardized way.

Images of changes

2025-01-17.02-38-00.mp4

Testing

Made above video.
Disassembled a custom vendor without a linked POS.
Deconstructed and destroyed a custom vendor with stuff in it. Got the stuff back both times.
Used an ATM, merch vendor, and claw machine (all the collateral migrations).

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Declaration

• I confirm that I either do not require pre-approval for this PR, or I have obtained such approval and have included a screenshot to demonstrate this below.

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Changelog

🆑
add: Custom vendors that you can load and buy from. The chef and bartender can buy a kit from their vendor, and they can be built with a vending machine board like any other vender, but don't require a restocking kit.
/:cl:

[FunnyMan3595]

Looks like we'll need #27784 to merge before this, since the migration on /obj/machinery/economy wasn't sufficient.