OnlineServices: Ensure HTTPManager is deleted before interface objects

[seer-by-sentry]

Fixes CLIENT-QP. The issue was that: HTTP request callback executes after its captured interface object is deleted during NGMP_OnlineServicesManager shutdown, causing use-after-free.

• Modified the NGMP_OnlineServicesManager destructor to delete the HTTPManager before deleting other interface objects.
• This ensures that completion callbacks invoked during HTTPManager::Shutdown() do not reference invalid interface objects.
• Cleared the completion callback in HTTPRequest after invocation to prevent use-after-free issues during shutdown.

This fix was generated by Seer in Sentry, triggered automatically. 👁️ Run ID: 2359009

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