Implement `MAP(key, value)` syntax to match documentation

### Describe the bug

[The documentation](https://datafusion.apache.org/user-guide/sql/scalar_functions.html#map) shows the `map` function supports a simple key-value syntax like `map(key, value)`, but this syntax currently errors!

```sql
DataFusion CLI v51.0.0
> SELECT MAP('type', 'test');
Execution error: Expected list, large_list or fixed_size_list, got Utf8
```