Rollup merge of #121236 - long-long-float:rust-fix-consider-slicing, r=Nadrieril

Don't show suggestion if slice pattern is not top-level

Close #120605

Don't show suggestion to add slicing (`[..]`) if the slice pattern is enclosed by struct like `Struct { a: [] }`.

For example, current rustc makes a suggestion as a comment. However, the pattern `a: []` is wrong, not scrutinee `&self.a`.
In this case, the structure type `a: Vec<Struct>` and the pattern `a: []` are different so I think the pattern should be fixed, not the scrutinee.
If the parent of the pattern that was the target of the error is a structure, I made the compiler not show a suggestion.

```rs
pub struct Struct {
    a: Vec<Struct>,
}

impl Struct {
    pub fn test(&self) {
        if let [Struct { a: [] }] = &self.a {
//             ^^^^^^^^^^^^^^^^^^   ------- help: consider slicing here: `&self.a[..]`
            println!("matches!")
        }
    }
}
```

Note:

* ~~I created `PatInfo.history` to store parent-child relationships for patterns, but this may be inefficient.~~
  * I use two fields `parent_kind` and `current_kind` instead of vec. It may not performance issue.
* Currently only looking at direct parents, but may need to look at deeper ancestry.

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