solve "Int64 with null value mangles large-ish integers" problem
- [x] closes #30268 
- [ ] tests added/passed
- [x] passes black pandas
- [x] passes git diff upstream/master -u -- "*.py" | flake8 --diff
- [x] whatsnew entry
The `pd.Series` was giving less precise output when inputting a list containing large integers and np.nan values and passing `dtype="Int64"`. Which was due to converting it to `np.array`. This PR aims to solve that bug.