HitSearcher is fetching data from Algolia already when just initially adding a stream listener

### **Describe the bug 🐛**

**TL;DR:**
Algolia backend gets called with a search immediately after adding a listener function to the response stream, even before actively starting a search by executing the `hitsSearcher.query(String query)` method.

**Long version:**

I'm following [Getting started with Flutter Helper](https://www.algolia.com/doc/guides/building-search-ui/getting-started/flutter/), but want to use `algolia_helper_flutter` without `infinite_scroll_pagination` and following clean architecture using the BLoC pattern.

I'm initializing the HitsSearcher in my BLoC constructor the common way like this:
```dart
_productsSearcher = HitsSearcher(applicationID: 'latency',
apiKey: '927c3fe76d4b52c5a2912973f35a3077',
indexName: 'STAGING_native_ecom_demo_products');
```

I also want to add a listener to the responses stream as soon as responses are coming in after queries.

I can do that with
```dart
_productsSearcher.responses.listen(_searchPageListener);
```

⚠️ **As soon as I call `listen()` to add the listener function, HitsSearcher executes a call to the Algolia backend. This I don't want, because I'm still in the setup phase in my BLoC constructor.**

This call is happening because when accessing the responses stream, this code is executed: `searchService.search(req.state)`:
https://github.com/algolia/algoliasearch-helper-flutter/blob/0b0154a5aed1a198239cc957ab05a68abbbe1d2a/helper/lib/src/searcher/hits_searcher.dart#L272

..which in turn executes this:
https://github.com/algolia/algoliasearch-helper-flutter/blob/0b0154a5aed1a198239cc957ab05a68abbbe1d2a/helper/lib/src/service/algolia_hits_search_service.dart#L77

### **To Reproduce 🔍**

1. Initialize HitsSearcher()
2. Add a listener function to the response stream
3. :x: See listener function being called immediately, even without a call to hitsSearcher.query() before.

### **Expected behavior 💭**
Algolia search does not get called immediately when adding the response listener, but only after calling searcher.query()

### **Environment:**

- OS: Android API 33
- Library Versions
- algolia_helper_flutter: 0.5.0 and algolia_helper_flutter: **^1.0.0-pre** as well

### **Additional context**
Thanks for supporting Flutter ❤️

Start in helper/lib/src/searcher/hits_searcher.dart at the responses stream behavior, then inspect helper/lib/src/service/algolia_hits_search_service.dart where the request is sent. Verify that adding a listener does not call Algolia before HitsSearcher.query(), while an explicit query still performs the search.

Written by the indexing model from the issue text.