[DDW-512] Fix and improve menu code for Windows and Linux

[DominikGuzei]

This PR fixes the broken app menu on windows and linux and also cleans up the code on the way by adding proper flow type checks.

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Review Checklist:

Basics

• PR is updated to the most recent version of target branch (and there are no conflicts)
• PR has good description that summarizes all changes and shows some screenshots or animated GIFs of important UI changes
• CHANGELOG entry has been added and is linked to the correct PR on GitHub
• Automated tests: All acceptance tests are passing (yarn run test)
• Manual tests (minimum tests should cover newly added feature/fix): App works correctly in development build (yarn run dev)
• Manual tests (minimum tests should cover newly added feature/fix): App works correctly in production build (yarn run package / CI builds)
• There are no flow errors or warnings (yarn run flow:test)
• There are no lint errors or warnings (yarn run lint)
• Text changes are proofread and approved (Jane Wild)
• There are no missing translations (running yarn run manage:translations produces no changes)
• UI changes look good in all themes (Alexander Rukin)
• Storybook works and no stories are broken (yarn run storybook)
• In case of dependency changes yarn.lock file is updated

Code Quality

• Important parts of the code are properly documented and commented
• Code is properly typed with flow
• React components are split-up enough to avoid unnecessary re-rendering
• Any code that only works in Electron is neatly separated from components

Testing

• New feature / change is covered by acceptance tests
• All existing acceptance tests are still up-to-date
• New feature / change is covered by Daedalus Testing scenario
• All existing Daedalus Testing scenarios are still up-to-date

After Review:

• Merge PR
• Delete source branch
• Move ticket to done on the Youtrack board

[DmitriiGaico]

Tested/Approved.