This diff does two things:
1. Updates `useGetMessageInfoForPreview` so that it falls back to the old behavior if it fails to find a message to preview that passes `showInMessagePreview`. This allows us to avoid showing "No messages". This is "Potential solution 2" described on Linear [here](https://linear.app/comm/issue/ENG-9556/hide-some-robotext-from-messagepreview#comment-62bdf153).
2. Updates `useGetMessageInfoForPreview` to also return `shouldFetchOlderMessages`, a flag that indicates to the caller if the fallback described above occurred. This will allow us to implement "Potential solution 3" from the Linear comment linked above.
Depends on D13829