Wrong type definition in the reported properties update function

# Context

- **OS and version used:** Debian 12
- **Node.js version:** 24
- **npm version:** not relevant
- **list of installed packages:** not relevant

## Description of the issue

There is a type definition issue inside the twin.ts implementation. I've copied the code sample below from here: https://github.com/Azure/azure-iot-sdk-node/blob/main/device/core/src/twin.ts#L181

1. in my opinion it's weird, that the update function is put onto the reported properties object only if `_clearCachedProperties ` is called
2. the `done` callback function has `err?: null` as parameter, which is passed as argument to `_updateReportedProperties` which has `done: (err?: Error)` in the signature -> **null vs Error type**
3. the update method is completely missing from the type definition, since it is added to the `reported` object at runtime and not before

## Code sample exhibiting the issue

```
private _clearCachedProperties(): void {
// eslint-disable-next-line @typescript-eslint/no-this-alias
const self = this;
this.properties = {
reported : {
update : function (state: any, done: (err?: null) => void): void {
self._updateReportedProperties(state, done);
}
},
desired : {
}
};
}
```

```
private _updateReportedProperties(state: any, done: (err?: Error) => void): void {
...
}
```

Start in device/core/src/twin.ts around _clearCachedProperties and _updateReportedProperties, including the reported-properties example at line 181. Trace the reported object’s type and callback signatures; done means the update method is represented in the type definition and its callback is compatible with _updateReportedProperties.

Written by the indexing model from the issue text.