ENH: Add ignore_index to sort_index
- [x] closes #30114
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry


@jreback 
I just looked back at #30114 and found out that i overlooked to add `ignore_index` to `sort_index`, and this might be the reason this issue is still left open. I added this to `sort_index` to close this issue.
Lgtm thanks! will do @jreback  Hi,`ignore_index = True` works  just fine and meets my expectations when `axis =0`,but when `axis = 1`, the number of index after reset using `ignore = Ture` is equal to the number of columns instead of the original index number,like `new_index = range(len(columns))`.
Is this a bug, or where am I going wrong?
THKS!