CORE-20124
Since `TB_HITTEST` returns negative numbers for ID for separator menu items [^1],
shell menu assumes mouse moved outside of the menu popup, highlighting the menu
item for currently open submenu.
To fix this behavior, we can detect separators in `CMenuFocusManager::ProcessMouseMove`
and negate the ID returned by `TB_HITTEST` to make it a positive number again,
so the shell menu wouldn't glitch.
[^1]: https://learn.microsoft.com/en-us/windows/win32/controls/tb-hittest
