…ple sheets

### What problem does this PR solve?
discussed in https://github.com/infiniflow/ragflow/pull/4102
- In excel_parser.py, `total` means the total number of rows in Excel,
but it return in the first iterate, that lead to the wrong `to_page`
- In table.py, it when Excel file has multiple sheets, it will be
divided into multiple parts, every part size is 3000, `data` may be
empty, because it has recorded in the last iterate.
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)