PERF: indexing on UInt64Index with int64s
- [x] closes #41873
- [ ] 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
- [ ] whatsnew entry

This fixes a regression on master so should be backported to 1.3.x @jbrockmendel can you post some timings. > can u add a test here

not actually changing any behavior

> can you post some timings

based on the asv mentioned in #41873

```
index = pd.UInt64Index(range(10**6))
ser = pd.Series(np.random.randn(10**6), index=index)

%timeit ser.loc[[800000]]
278 µs ± 12.3 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)   # <- PR
124 ms ± 1.13 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)   # <- master
``` @meeseeksdev backport 1.3.x Something went wrong ... Please have  a look at my logs.