[Brave News]: Show RSS feed in small cards if image not available

[LorenzoMinto]

Description

When an RSS image cannot be fetched we should display it as a small card in the feed so it doesn't look as broken. As a follow up, it might be worth investigating why certain rss feeds' images are not fetched.

Steps to reproduce

1. Subscribe to RSS feed (i.e. https://astro.build/ -- subscribe through omnibox)
2. Open direct feed in left sidebar

Actual result

Expected result

Only small cards should be used.

Reproduces how often

Easily reproduced

Brave version (brave://version info)

NA

Channel information

• [x] release (stable)
• [x] beta
• [x] nightly

Reproducibility

• [ ] with Brave Shields disabled
• [ ] with Brave Rewards disabled
• [ ] in the latest version of Chrome

Miscellaneous information

No response