vlib: add mut for the first parameter of builtin.copy, arrays.copy and crypto (#13702)

vlib/net/http/request_test.v

@@ -14,7 +14,7 @@ fn (mut s StringReader) read(mut buf []byte) ?int {
 	}
 	max_bytes := 100
 	end := if s.place + max_bytes >= s.text.len { s.text.len } else { s.place + max_bytes }
-	n := copy(buf, s.text[s.place..end].bytes())
+	n := copy(mut buf, s.text[s.place..end].bytes())
 	s.place += n
 	return n
 }

vlib/net/urllib/urllib.v

@@ -274,7 +274,7 @@ fn escape(s string, mode EncodingMode) string {
 	required := s.len + 2 * hex_count
 	mut t := []byte{len: required}
 	if hex_count == 0 {
-		copy(t, s.bytes())
+		copy(mut t, s.bytes())
 		for i in 0 .. s.len {
 			if s[i] == ` ` {
 				t[i] = `+`