Add `useless_concat`

### What it does

Checks for the use of `concat!("takes a single string literal")`.

### Advantage

Redundant code. The type of a literal yielded by `concat!` and the type of a string literal are both `&'static str`.

### Drawbacks

_No response_

### Example

```rust
let foo = concat!("foo");
```

Could be written as:

```rust
let foo = "foo";
```
