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

vlib/builtin/array.v

@@ -816,7 +816,7 @@ pub fn (b []byte) hex() string {
 // Returns the number of elements copied.
 // NOTE: This is not an `array` method. It is a function that takes two arrays of bytes.
 // See also: `arrays.copy`.
-pub fn copy(dst []byte, src []byte) int {
+pub fn copy(mut dst []byte, src []byte) int {
 	min := if dst.len < src.len { dst.len } else { src.len }
 	if min > 0 {
 		unsafe { vmemmove(&byte(dst.data), src.data, min) }