Implicit broadcasting for SIMD arrays

[Barinzaya]

This covers broadcasting from untyped numbers when converting to a #simd vector, as well as when performing binary operations. This mirrors the way this logic works with regular fixed arrays (except untyped strings won't be converted). SIMD intrinsics, which have special logic for handling their inputs, have not been adjusted.

A simple example of usage (which worked for fixed arrays, but would have been erroneous with #simd):

package test
import "core:fmt"
main :: proc () {
	a : #simd[4]u32 = 2
	b : u32 = 3
	fmt.println(b * a + 1) // <7, 7, 7, 7>
}