fix: add `num_proc` argument to `Dataset.to_sql`
Hi ! could you also write a test to make sure this works fine ?

(in case there needs to be a special logic to handle the concurrent writes to the database) Hi @lhoestq 
Done! Let me know if more is needed :)
**Task Done:** 

- Resolve issue #7788 : Add the missing argument mapping in Dataset.to_sql (`src/datasets/arrow_dataset.py`)


