feat: Add support for per-context summary events. (#247)

Updates to 1.9.0 of the common client library to support per-context
summary events.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Single dependency version bump with no direct code changes; risk is
limited to behavior changes introduced by `launchdarkly_common_client`
1.9.0.
> 
> **Overview**
> Bumps the Flutter SDK’s dependency on `launchdarkly_common_client`
from `1.8.0` to `1.9.0` to pick up updated common-client behavior (e.g.,
per-context summary events support).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
622fe03. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: kinyoklion

packages/flutter_client_sdk/pubspec.yaml

@@ -13,7 +13,7 @@ dependencies:
     sdk: flutter
   package_info_plus: ">=4.2.0 <10.0.0"
   device_info_plus: ">=9.1.1 <13.0.0"
-  launchdarkly_common_client: 1.8.0
+  launchdarkly_common_client: 1.9.0
   shared_preferences: ^2.2.2
   connectivity_plus: ">=5.0.2 <8.0.0"
   web: ^1.1.1