fix manifest statistics: added_files_count, deleted_files_count and existing_files_count

[chenzl25]

• added_data_files_count should be changed to added_files_count
• existing_data_files_count should be changed to existing_files_count
• deleted_data_files_count should be changed to deleted_files_count
  as the spec https://arc.net/l/quote/rlusxtoo

Otherwise, spark would filter the manifest if added_files_count equals 0

[Xuanwo]

Thanks for the PR, but this repo doesn't accept any PRs anymore. Sorry for the inconvenience.

Read more about this in #279

[chenzl25]

It is a critical fix 🥵

[Xuanwo]

It is a critical fix 🥵

I apologize for the inconvenience. I understand that this happens. The best solution might be to fork icelake so you can continue using and modifying it before we finish the migration to iceberg-rust.