Add indicator for modified post meta in pre-publish flow

[artemiomorales]

What problem does this address?

Follow up to #61811

While we are now indicating to users when metadata has changed to published posts, we do not yet do so when a post is still in pre-published state.

We should determine what this UX should be and any revisions that would be needed to accommodate this in the pre-publish flow.

What is your proposed solution?

One idea: We can consider integrating information about the post meta in the pre-publish check as another collapsed panel next to suggestions related to tags and categories, as observed in this comment.

We should also consider surfacing this information whenever a draft is saved.