IDEA-383444 Keep existing dependencies in sync contributors

[akerimsenol]

Note

Introduces GradleDependencySyncExtension to keep existing module dependencies and SDKs during Gradle sync and registers it in the plugin.

• Gradle Sync:
  • New Extension: Add GradleDependencySyncExtension to retain existing ModuleEntity dependencies during sync, prioritizing explicit SdkDependency and falling back to inherited SDK.
  • Registration: Register the extension in plugins/gradle/plugin-resources/META-INF/plugin.xml.

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[nskvortsov]

Please add tests covering this fix