Remove thumbnail progress indicators

[micahmo]

Pull Request Description

This PR removes some usage of loading indicators (CircularProgressIndicator).

Currently, there are loading indicators for images and link previews. On Android, these indicators are incosistent in size and thickness, and on iOS, they're totally different styles. They give the general impression that things are constantly loading. In other apps, there are no such indicators; images just fade in when available. In my opinion (again, this is just a matter of preference) that looks much cleaner.

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Before

qemu-system-x86_64_EEZxVVooTn.mp4

After

qemu-system-x86_64_60q4u8kheK.mp4

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[ajsosa]

Personally I like this change and would prefer it, but maybe we should get some feedback from @hjiangsu and others.

[CTalvio]

Personally I like this change and would prefer it, but maybe we should get some feedback from @hjiangsu and others.

I also think it makes sense.

[machinaeZER0]

I love it! Any extra performance benefit from this change? Either way it seems like a good one to me :)

[micahmo]

Any extra performance benefit from this change?

No, this is just cosmetic. But in my opinion it does feel better.😊

[hjiangsu]

Yeah, after looking at the video previews, it does look better.

I'll approve this and merge it in once the merge conflicts are fixed!

[micahmo]

All set!