[WIP] Refactored webext-storage database close function

[lougeniaC64]

This is so not ready for primetime . . . enter at your own risk.

Pull Request checklist

• Breaking changes: This PR follows our breaking change policy
  • [ ] This PR follows the breaking change policy:
    • This PR has no breaking API changes, or
    • There are corresponding PRs for our consumer applications that resolve the breaking changes and have been approved
• [ ] Quality: This PR builds and tests run cleanly
  • Note:
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• [ ] Tests: This PR includes thorough tests or an explanation of why it does not
• [ ] Changelog: This PR includes a changelog entry in CHANGELOG.md or an explanation of why it does not need one
  • Any breaking changes to Swift or Kotlin binding APIs are noted explicitly
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  • Any new dependencies are accompanied by a summary of the due diligence applied in selecting them.

Branch builds: add [firefox-android: branch-name] to the PR title.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 21.73%. Comparing base (79df7fe) to head (125d8aa).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6424   +/-   ##
=======================================
  Coverage   21.73%   21.73%           
=======================================
  Files         344      344           
  Lines       31132    31132           
=======================================
  Hits         6768     6768           
  Misses      24364    24364           

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