BUG: json.decode fails for nums larger than sys.maxsize
- [x] closes #20599 
- [x] tests added
- [ ] tests passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Follow-up to #34473 
@WillAyd I've made some headway on this. I've fixed `decode_numeric`
https://github.com/pandas-dev/pandas/blob/f5b2e5a9a2431165b1e8002219c5d3962d7bc920/pandas/_libs/src/ujson/lib/ultrajsondec.c#L117
so that for `intValue`, the variable into which we read the incoming int,  when it overflows it's reset rather than throwing a `ValueError`. If I understand this we'd want to store these pre-reset `intValues` in some way and then combine them into a PyLong object in `Object_newBigNum`.

Is that right, and if yes what's the best way to go forward? For example, would we want to use a `wide_char` similarly to what's done for string?
https://github.com/pandas-dev/pandas/blob/f5b2e5a9a2431165b1e8002219c5d3962d7bc920/pandas/_libs/src/ujson/python/JSONtoObj.c#L452 Closing for now. I'll open a new request when I've got something ready for review @arw2019 Did you ever create a new PR, by any chance? Thanks to your MR #34473, I'm able to write out large numbers to JSON. But, I can't read them back in. > @arw2019 Did you ever create a new PR, by any chance? Thanks to your MR #34473, I'm able to write out large numbers to JSON. But, I can't read them back in.

I have an unfinished PR in the works, planning to finish it soon-ish (1.2 is probably a stretch, next release more likely) - unless you'd like to do a PR?