Show progress indicator during post refresh

[micahmo]

Pull Request Description

This PR fixes a small quirk of the experimental/new post page that has been "bothering" me for a while. The quirk is that while the comments are loading, the spinner goes away before the comments are fully loaded and there is a brief pause. I've tried to capture it in the screen recording below, but the pause is much "worse" when you're on a slower network (which is what implied to me that there was still something loading, as opposed to just being a visual/layout glitch).

Turns out all I had to do was handle an additional state, and it looks much better now!

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Before

qemu-system-x86_64_xwVJB3SlJS.mp4

After

qemu-system-x86_64_m6noSFAa5F.mp4

Checklist

• If a new package was added, did you ensure it uses an appropriate license and is actively maintained?
• Did you use localized strings (and added appropriate descriptions) where applicable?
• Did you add semanticLabels where applicable for accessibility?

[hjiangsu]

LGTM!

[micahmo]

Hey @hjiangsu I just noticed that this change causes the comments to "reload" when you do something like upvote or save. Would you be able to roll this back and I'll work on a better solution.