crypto: add custom errors to crypto lib (#9522)

vlib/crypto/rand/rand_windows.c.v

@@ -19,7 +19,7 @@ pub fn read(bytes_needed int) ?[]byte {
 	// use bcrypt_use_system_preferred_rng because we passed null as algo
 	status := C.BCryptGenRandom(0, buffer.data, bytes_needed, bcrypt_use_system_preferred_rng)
 	if status != status_success {
-		return read_error
+		return IError(&ReadError{})
 	}
 	return buffer
 }