fix: Enrollment API call after purchase.

[farhan-arshad-dev]

Description

LEARNER-9312 LEARNER-9315

• Fix Error modal on My Courses after completing IAP flow from Course Dashboard.
• Check Unfulfilled Purchases only On live server calls for my courses and Once per app session.
• Fix the Refresh Now button action.
• Validate SKU onPurchaseComplete for billing processor.
• Fix Warning: Webview has been destroyed after an event is fired.
• Update the Refresh event to update my course list after in-app purchases.

ps: Issue LEARNER-9312 is not reproducible on the dev side, so the fix is scenario-based.