BUG: UInt64Index.where with int64 value
- [ ] closes #xxxx
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

bug? needs a release note. I would put in 1.3 for now. (it can be moved if needed after @jreback reviews)

using semver we can make backwards compatible bug fixes in patch releases but we tend to only fix regressions.

from https://semver.org/

Given a version number MAJOR.MINOR.PATCH, increment the:

MAJOR version when you make incompatible API changes,
MINOR version when you add functionality in a backwards compatible manner, and
PATCH version when you make backwards compatible bug fixes.

 this is fine for 1.3 @meeseeksdev backport 1.3.x Something went wrong ... Please have  a look at my logs.