Add usePostPrePublishValue hook

[manzoorwanijk]

In a task like #550, we need to preserve some value before the post is publish, to avoid the value being updated after the post is published.

This PR creates a hook named usePostPrePublishValue, which watches for a passed value until the post is published and freezes the value after that.

Proposed changes:

• Create usePostPrePublishValue hook
• Extract re-usable test logic from the tests for useSyncPostDataToStore to common utilities
• Add unit tests for usePostPrePublishValue hook

Other information:

• Have you written new tests for your changes, if applicable?
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Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Since the hook is not used yet, just verify that tests pass and CI is happy
• You may test it via Social: Hide share status when no connection is enabled #39120

[github-actions]

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[github-actions]

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[spsiddarthan]

Seems reasonable to me. I disabled the auto-merge though, so we can get it merged in the morning to avoid any surprises. Seems safe though since it's a new hook being introduced.