all: change optional to result in most of the libraries (#16123)

vlib/arrays/README.md

@@ -9,8 +9,8 @@ import arrays
 
 fn main() {
 	a := [1, 5, 7, 0, 9]
-	assert arrays.min(a)? == 0
-	assert arrays.max(a)? == 9
-	assert arrays.idx_min(a)? == 3
+	assert arrays.min(a)! == 0
+	assert arrays.max(a)! == 9
+	assert arrays.idx_min(a)! == 3
 }
 ```