fix: save scroll position on exit from video xblock fullscreen mode

[ihor-romaniuk]

This merge request contains a fix for toggling video xblock full-screen mode and saving the previous window top offset position on exit from the full-screen state.

A related bug was found here https://bugs.chromium.org/p/chromium/issues/detail?id=142427 but it still reproduces.

Realised solution: Save the scroll position before the turn on the fullscreen mode and scroll to the previous position on turn off the fullscreen mode.

Dependent PR to MFE Learning:
This MR openedx/edx-platform#32306 must be merged with this MR.

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (open-release/palm.master@757d967). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

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  Hits                                ?     3803           
  Misses                              ?      549           
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[itsjeyd]

Part of a set of PRs for openedx/platform-roadmap#229.

[leangseu-edx]

LGTM 👍

[openedx-webhooks]

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