Auto merge of #8631 - Alexendoo:splitn-overlap, r=xFrednet

Remove overlap between `manual_split_once` and `needless_splitn`

changelog: Remove overlap between [`manual_split_once`] and [`needless_splitn`]. Fixes some incorrect `rsplitn` suggestions for [`manual_split_once`]

Things that can trigger `needless_splitn` no longer trigger `manual_split_once`, e.g.

```rust
s.[r]splitn(2, '=').next();
s.[r]splitn(2, '=').nth(0);
s.[r]splitn(3, '=').next_tuple();
```

Fixes some suggestions:

```rust
let s = "should not match";

s.rsplitn(2, '.').nth(1);
// old -> Some("should not match")
Some(s.rsplit_once('.').map_or(s, |x| x.0));
// new -> None
s.rsplit_once('.').map(|x| x.0);

s.rsplitn(2, '.').nth(1)?;
// old -> "should not match"
s.rsplit_once('.').map_or(s, |x| x.0);
// new -> early returns
s.rsplit_once('.')?.0;
```

0 files changed, 0 insertions, 0 deletions