Refactor tables latex
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

As suggested [here](https://github.com/pandas-dev/pandas/pull/35284#issuecomment-665273834), utils fonctions which begin or end tables / tabulars / longtables environments could be merged. 