View contents of payload blocks

[buthed010203]

Allows players to view the contents of blocks on payload conveyors as well as take and remove items from them. Additionally introduces a Shift + Click to take full stack when taking items from a block. Also adds env vars for steamtest's move destination and out file name.

Heres an example of it in action: https://mee6.is-terrible.com/5dd4e51OD.webm This item display might be worth changing now? Idk, probably not.

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• [x] I have ensured that any new features in this PR function correctly in-game, if applicable.