convert holoposter to TGUI

[intercepti0n]

About The Pull Request

I've converted holoposter selection screen to TGUI plus centered item icon in vending machine UI.

Why It's Good For The Game

Holoposter selection now has an UI with an amazing preview picture.

Testing

Changelog

🆑
refactor: converted holoposter to TGUI.
/:cl:

[MLGTASTICa]

nice work

[itchybones]

Welp, you beat me to it. 👍

[hyperioo]

If you want to improve holoposter a bit more, you could replace the Process() by a proc listening to a signal that fires once per minute, I think we have one. That would avoid Process calls every tick for no real use (especially if icon is forced).