feat: Add Dio HttpClientAdapter to ClientOptions

[techouse]

This PR gives the user the ability to optionally provide a custom Dio HttpClientAdapter, i.e.

final SearchClient client = SearchClient(
  appId: 'latency',
  apiKey: '6be0576ff61c053d5f9a3225e2a90f76',
  defaultHosts: () => const [
    Host(url: 'latency-dsn.algolia.net'),
    Host(url: 'latency-1.algolianet.com'),
  ],
  options: ClientOptions(
    httpClientAdapter: NativeAdapter(), // <-- from https://pub.dev/packages/native_dio_adapter
  ),
);

Via this option users can configure Dio to use native_dio_adapter which uses cupertino_http on iOS and cronet_http on Android to delegate HTTP requests to the native platform instead of the dart:io platforms.

The advantages of using cronet_http are:

• It automatically supports Android platform features such as HTTP proxies.
• It supports configurable caching.
• It supports more HTTP features such as HTTP/3.

The advantages of using cupertino_http are:

• It automatically supports iOS/macOS platform features such VPNs and HTTP proxies.
• It supports many more configuration options such as only allowing access through WiFi and blocking cookies.
• It supports more HTTP features such as HTTP/3 and custom redirect handling.

---

Addresses #12

[techouse]

Superseded by algolia/api-clients-automation#3290