transformer: missing initializer for TypeScript class constructor arguments with `private` modifier

Discovered this when bundling Vue via Rolldown:

In
```ts
class Foo {
  constructor(public foo, private bar) {}
}
```

Out
```js
class Foo {
  constructor(foo, bar) {
    this.foo = foo
    // !!! `this.bar = bar` is missing
  }
}
```

Expected
```js
class Foo {
  constructor(foo, bar) {
    this.foo = foo
    this.bar = bar
  }
}
```