feat: dispatch FocusEvent in hidden documents

[ph-fritsche]

What:

Dispatch focus, focusin, blur and focusout events when document.visibilityState is hidden.

Why:

Browsers don't dispatch focus events on hidden windows.
Our simulation of the UI layer relies on these events and userEvent should act like a user does on a visible window.

How:

Patch HTMLElement.focus() and HTMLElement.blur() and dispatch the events if the document is hidden.

Checklist:

• Tests
• Ready to be merged

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[github-actions]

🎉 This PR is included in version 14.6.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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[donaldpipowitch]

It looks like this change broke some integrations. See #1258. For me it broke react-aria here:

https://github.com/adobe/react-spectrum/blob/4b8b33a022a17c7df2d6ee6d23b6208b503973fe/packages/%40react-aria/interactions/src/useFocusVisible.ts#L138

TypeError: Cannot set property focus of [object HTMLElement] which has only a getter

I have to stick with 14.5.2 for now.