[macOS] Make sure macOS behaves correctly when calling hide()

[fdennis]

Fixes #431

[vrescobar]

I tried the fix, with a direct rebase on the main from this one and works perfectly. The fix is totally valid and trivial to understand and no conflicts to rebase.

  window_manager:
    path: ../third_party/window_manager/packages/window_manager

@lijy91 can you rebase and merge? otherwise we need to keep always this sort of thing at the pubspec.yaml