Fix formatting of lambda star arguments (#6257)

## Summary
Previously, the ruff formatter was removing the star argument of
`lambda` expressions when formatting.

Given the following code snippet
```python
lambda *a: ()
lambda **b: ()
```
it would be formatted to
```python
lambda: ()
lambda: ()
```

We fix this by checking for the presence of `args`, `vararg` or `kwarg`
in the `lambda` expression, before we were only checking for the
presence of `args`.

Fixes #5894

## Test Plan

Add new tests cases.

---------

Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

crates/ruff_python_formatter/src/expression/expr_lambda.rs

@@ -22,7 +22,8 @@ impl FormatNodeRule<ExprLambda> for FormatExprLambda {
 
         write!(f, [text("lambda")])?;
 
-        if !parameters.args.is_empty() {
+        if !parameters.args.is_empty() || parameters.vararg.is_some() || parameters.kwarg.is_some()
+        {
             write!(
                 f,
                 [