Suggest use `to_string` rather than `format!("{}")`

### What it does

Sometime, people are using `format!("{}")` to stringify an object, which can be rewritten in `.to_string()` to keep code clean.

### Lint Name

_No response_

### Category

style

### Advantage

_No response_

### Drawbacks

_No response_

### Example

```rust
let a = format!("{}", x);
```

Could be written as:

```rust
let a = x.to_string();
```
