useFocusOnMount: add ability to handle focus at every render

[afercia]

Description

There are legitimate cases where a component needs to handle initial focus at every render.

For example, some of the 'Welcome guide' modal dialogs do have 'steps' to show new content within the modal dialog. When a new step is rendered, the modal dialog needs to set focus again at the top of the fcontent: preferably set focus to the modal dialog container itself.

#52300 implemented such behavior via an ad-hoc implementation in the Guide component. I'm thinking this behavior should be handled by useFocusOnMount instead, to avoid ad-hoc implementations and avoid almost-duplicate functionality and code.

Any thoughts welcome.

Step-by-step reproduction instructions

• Go to the Post editor > Options > Welcome guide
• Observe initial focus is set to the modal dialog container: Press Tab and observe focus foes to the Close button.
• Click 'Next' to go to the next step.
• Observe initial focus is set to the modal dialog container: Press Tab and observe focus foes to the Close button.
• Same when clicking 'Previous'.
• Observe thie focus behavior is currently handled via an ad-hoc implementation in the Guide component.
• Observe that useFocusOnMount runs regardless because it uses the default value true.

Screenshots, screen recording, code snippet

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Environment info

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Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes