codebase reorganization of some folders

[silicons]

moves & renames _onclick and _rendering to click and rendering and moves _onclick/hud to rendering/legacy_hud
moves those to game folder

Why?

because i don't think the root /code folder having them is correct
what the idea is is that:

• /code/game has 'whole game' stuff that should depend on as little else as possible (can't avoid stuff like subsystems atmos and tgui obviously so this is a loose suggestion); this is more aimed at that we shouldn't have, say, a hypospray in here when hyposprays are logically part of the reagents module since hyposprays don't work without reagents and are primarily content for engaging with the reagents module
• /code/modules are standalone 'modules' that contain a tightly related subset of the game, e.g. chemistry, maploader/management systems, etc.
• /code/controllers are core systems; many of them rely on / utilize stuff from game/modules (duh) but they're here forever since they're important
• /code/datums are mostly just helper datums; object/item/whatever-specific datums should be stored in their given files.