Simplify spreads of inline arrays

[Schaeff]

There is a memory blowup in the way we desugar spreads:

size(...a) = n * size(a)

because

...a = a[0], ..., a[n] <-- we have to copy a n times when we desugar

but if a is an inline value like [0, 1, 2]

size(a) = O(n)

With this change, we desugar ...a when a is an inline array to the content of the array:

...[x, y, z] = x, y, z

The program

def main() -> ():
	field[3] a = [...[...[...[0, 0, 0]]]]
	return

Before this change:

def main() -> ():
	field[3] _a_0
	_a_0 = [[[[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][0], [[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][1], [[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][2]][0], [[[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][0], [[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][1], [[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][2]][1], [[[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][0], [[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][1], [[0, 0, 0][0], [0, 0, 0][1], [0, 0, 0][2]][2]][2]]
	return 

After this change:

def main() -> ():
	field[3] _a_0
	_a_0 = [0, 0, 0]
	return 

Replaces #462 which ends up being too complex of an approach.

[JacobEberhardt]

Low-hanging fruit, nice!