fix: App Crashing on background for IAP users

[farhan-arshad-dev]

fixes: LEARNER-9527

Description

LEARNER-9527

• Fix app Crashing in the background for IAP users
• Use CancellableContinuation instated of Continuation.
• Resume continuation with results if active and not completed.
• Fix Issue NullPointerException on CourseComponent#isVideoBlock() for CourseUnitNavigationActivity

Steps to reproduce the crash.

• Open the app with IAP enabled.
• Force stop the Google play store app.
• edx App leads to the crash.

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% :warning:

Comparison is base (5b3043d) 1.13% compared to head (32754c8) 1.13%. Report is 1 commits behind head on rc/4.1.1.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## rc/4.1.1 #1813 +/- ## ============================================= - Coverage 1.13% 1.13% -0.01% Complexity 137 137 ============================================= Files 534 535 +1 Lines 25186 25195 +9 Branches 3039 3042 +3 ============================================= Hits 286 286 - Misses 24873 24882 +9 Partials 27 27 ``` | [Files Changed](https://app.codecov.io/gh/openedx/edx-app-android/pull/1813?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openedx) | Coverage Δ | | |---|---|---| | [.../java/org/edx/mobile/extenstion/ContinuationExt.kt](https://app.codecov.io/gh/openedx/edx-app-android/pull/1813?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openedx#diff-T3BlbkVkWE1vYmlsZS9zcmMvbWFpbi9qYXZhL29yZy9lZHgvbW9iaWxlL2V4dGVuc3Rpb24vQ29udGludWF0aW9uRXh0Lmt0) | `0.00% <0.00%> (ø)` | | | [.../org/edx/mobile/inapppurchases/BillingProcessor.kt](https://app.codecov.io/gh/openedx/edx-app-android/pull/1813?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openedx#diff-T3BlbkVkWE1vYmlsZS9zcmMvbWFpbi9qYXZhL29yZy9lZHgvbW9iaWxlL2luYXBwcHVyY2hhc2VzL0JpbGxpbmdQcm9jZXNzb3Iua3Q=) | `0.00% <0.00%> (ø)` | | | [.../edx/mobile/view/CourseUnitNavigationActivity.java](https://app.codecov.io/gh/openedx/edx-app-android/pull/1813?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openedx#diff-T3BlbkVkWE1vYmlsZS9zcmMvbWFpbi9qYXZhL29yZy9lZHgvbW9iaWxlL3ZpZXcvQ291cnNlVW5pdE5hdmlnYXRpb25BY3Rpdml0eS5qYXZh) | `0.00% <0.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/openedx/edx-app-android/pull/1813/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openedx)

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