Add missing item alias metatables to async environment

[sfan5]

originals:

minetest/builtin/game/register.lua

Lines 33 to 41 in e92a217

	local alias_metatable = {
	__index = function(t, name)
	return rawget(t, core.registered_aliases[name])
	end
	}
	setmetatable(core.registered_items, alias_metatable)
	setmetatable(core.registered_nodes, alias_metatable)
	setmetatable(core.registered_craftitems, alias_metatable)
	setmetatable(core.registered_tools, alias_metatable)

and

minetest/builtin/game/register.lua

Lines 178 to 179 in e92a217

	-- Disable all further modifications
	getmetatable(itemdef).__newindex = {}

To do

This PR is Ready for Review.

How to test

• observe CI