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

vlib/crypto/rand/rand_default.c.v

@@ -4,6 +4,6 @@
 module rand
 
 // read returns an array of `bytes_needed` random bytes read from the OS.
-pub fn read(bytes_needed int) ?[]u8 {
+pub fn read(bytes_needed int) ![]u8 {
 	return error('rand.read is not implemented on this platform')
 }