Rework struct initializers

[Victorious3]

To avoid some ambiguity in the grammar and being able to use {} for blocks only, it's probably a good idea to change struct initializers to use the [] syntax.

The type of [] would depend on the elements provided.

	Element	Kind	Resulting type
1	[]	empty tuple	()
2	[1, 2, 3]	static array	[3; int]
3	[1, 2.0, 3]	tuple	(int, double, int)
4	[b = 20]	structure	struct { b: int }
5	[1, 2, b = 20]	initializer	Initializer([2; int], struct { b: int })
6	[1, 1.5, b = 20]	initializer (jagged)	Initializer((int, double), struct { b: int })
7	[(1) = 20, (2) = 30]	initializer map	InitializerMap([2; int], [2; int])
8	[(1) = 20, (1.5) = 2.5]	initializer map (jagged)	InitializerMap((int, double), (int, double))

Coercion table

↱	1	2	3	4	5	6	7	8
1	x	x	x	x	x	x	x	x
2		x	x
3			x
4				x	x	x
5					x	x
6						x
7							x	x
8								x

Struct initialization could be done using 1-6. Array initialization could be done with 1-3.

// Typed map
def make_map(type K, type V) -> Map(K, V)
def make_map(init: InitializerMap([type K], [type V])) -> Map(K, V)

// Untyped table
def make_table(init: Initializer(type K, type V)) -> Table
def make_table(init: InitializerMap(type K, type V)) -> Table