ffi version ^2.2.0 and above support

### Version of the agora_rtc_engine

6.6.3

### Platforms affected

- [x] Android
- [x] iOS
- [ ] macOS
- [ ] Windows
- [ ] Web

### Steps to reproduce

share_plus: ^13.2.0 and agora_rtc_engine: ^6.6.3 in the pubspec.yaml

### Expected results

Package successfully updated.

### Actual results

```
Because no versions of share_plus match >13.2.0 <14.0.0 and share_plus 13.2.0 depends on ffi ^2.2.0, share_plus ^13.2.0 requires ffi ^2.2.0.
And because agora_rtc_engine >=6.6.2-rc.1 depends on ffi ^1.1.2, share_plus ^13.2.0 is incompatible with agora_rtc_engine >=6.6.2-rc.1.
So, because sprint_conversations depends on both agora_rtc_engine ^6.6.3 and share_plus ^13.2.0, version solving failed.
```

### Code sample

Code sample

```dart
[Paste your code here]
```

### Screenshots or Video

Screenshots / Video demonstration

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### Logs

Logs

```console
[Paste your logs here]
```

### Flutter Doctor output

Doctor output

```console
[✓] Flutter (Channel stable, 3.44.4, on Microsoft Windows [Version 10.0.26200.8655], locale en-IN)
[✓] Windows Version (11 Home Single Language 64-bit, 25H2, 2009)
[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0)
[✓] Chrome - develop for the web
[✗] Visual Studio - develop Windows apps
✗ Visual Studio not installed; this is necessary to develop Windows apps.
Download at https://visualstudio.microsoft.com/downloads/.
Please install the "Desktop development with C++" workload, including all of its default components
[✓] Connected device (4 available)
[✓] Network resources
```

Start with pubspec.yaml and reproduce dependency resolution using share_plus ^13.2.0 and agora_rtc_engine ^6.6.3. Inspect the ffi constraints for the Agora package, then verify that the dependency solver can resolve ffi ^2.2.0 while retaining Android and iOS support. Done means the listed package versions update successfully without version-solving conflicts.

由索引模型根据 Issue 内容生成。