feat: add construct global for constructing arbitrary types & Union type

[makspll]

Makes this possible:

local type = world.get_type_by_name("SimpleEnum")

-- Struct Variant
local constructed = construct(type, {
    variant = "Struct",
    foo = 123
})

assert(constructed:variant_name() == "Struct", "Value was constructed incorrectly, expected constructed.variant to be Struct but got " .. constructed:variant_name())
assert(constructed.foo == 123, "Value was constructed incorrectly, expected constructed.foo to be 123 but got " .. constructed.foo)


-- TupleStruct Variant
local constructed = construct(type, {
    variant = "TupleStruct",
    _1 = 123
})

assert(constructed:variant_name() == "TupleStruct", "Value was constructed incorrectly, expected constructed.variant to be TupleStruct but got " .. constructed:variant_name())
assert(constructed._1 == 123, "Value was constructed incorrectly, expected constructed._1 to be 123 but got " .. constructed._1)

-- Unit Variant
local constructed = construct(type, {
    variant = "Unit"
})

assert(constructed:variant_name() == "Unit", "Value was constructed incorrectly, expected constructed.variant to be Unit but got " .. constructed:variant_name())

[makspll]

There's a gotcha with tuples, which can be constructed but need FromReflect manually registered bevyengine/bevy#17981