fix: perf problem of Action flyout menu

[yeze322]

Description

#minor

Problem When moving cursor around Action flyout menu, whole UI stuck.

Root cause
According to this issue microsoft/fluentui#5642 , when loading FluentUI's ContextualMenu, browser's focus state will be affected unexpectedly. In our case, when using the Action flyout menu, the browser focus state (triggered by onFocus and onBlur event) would be changed repeatedly for multiple (around 20) times.

Unfortunately, the browser's focus state was saved as a React state in DesignPage and post to Electron via IPC to enable/disbale the Electron app menu. As a result, everytime user moves cursor around the flyout menu, the design page will be redraw for tons of times which led to the UI stuck.

Solution
This PR fixes this issue by saving the focus state as a ref by using useRef() hook rather than useState().
Instead of subscribing the focus state change with useEffect(), whenever the ref is updated, now Composer will proactively report status to Electron app menu.

With this fix, DesignPage won't be redraw when the browser focus state changes.

Task Item

Screenshots

[coveralls]

Coverage decreased (-0.02%) to 55.339% when pulling d33c5f5 on yeze322:electron/flyout-perf into e8d0d55 on microsoft:main.