PERF: Delay creation of indexer in RangeIndex.sort_values
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added an entry in the latest `doc/source/whatsnew/v1.6.0.rst` file if fixing a bug or adding a new feature.

```
In [2]: ri = pd.RangeIndex(1_000_000)

In [3]: %memit ri.sort_values() # PR
peak memory: 120.22 MiB, increment: 0.10 MiB

In [4]: %memit ri.sort_values() # main
peak memory: 119.88 MiB, increment: 0.17 MiB
```
thx @mroeschke 