message: builder: fix panic on building big file
  Panic when the size of a regular file exceeds 4GB:
  ```
  thread 'main' panicked at 'attempt to multiply with overflow': src/bin/nydus-image/core/node.rs:371
  ```
  Fix it by changing `(chunk_size * i) as u64` to `chunk_size as u64 * i as u64`.
diff: @@ -368,7 +368,7 @@ impl Node {
  let file_offset = i as u64 * chunk_size as u64;
  let uncompressed_size = if i == self.inode.child_count() - 1 {
  (self.inode.size() as u64)
  - .checked_sub((chunk_size * i) as u64)
  + .checked_sub(chunk_size as u64 * i as u64)
  .ok_or_else(|| {
  anyhow!("the rest chunk size of inode is bigger than chunk_size")
  })? as u32
  