BUG: Fix lost precision when reading from Oracle Number column GH34988
Fixes: https://github.com/pandas-dev/pandas/issues/34988

- [x] closes #34988
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [x] whatsnew entry

This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Thanks for the pull request, but appears it has gone stale. If you'd like to continue, please address the review, move the whatsnew note to v.1.5 and we can reopen