[Brave News]: Improve peeking card selection

[LorenzoMinto]

Spec: https://docs.google.com/document/d/1HH7pohTPp-8uqdccwK4phOrwqK0-NRo-kkBxTDuWUsM/edit#heading=h.tlm8bpd2rbjl

Release notes:

Improved peeking card algorithm in Brave News to show more relevant articles

Test Plan:

Hard to actually test that the new algorithm is working as expected, but:

1. Peeking card should still show up on the NTP when Brave News is enabled
2. Refreshing the feed should generate a new peeking card

[LaurenWags]

@brave/qa-team along side the test plan from #35659 (comment), generally confirm that Brave News is still working

[MadhaviSeelam]

Verification PASSED using

Brave | 1.72.85 Chromium: 130.0.6723.58 (Official Build) beta (64-bit)
-- | --
Revision | 2c872aa4d2694bc73ec58e3b14538a4008a6381e
OS | Windows 11 Version 23H2 (Build 22631.4317)

1. Installed 1.72.85
2. launched Brave
3. News peak button is shown as expected
4. enabled News via NTP
5. news feed loaded as expected for default For You
6. opened a new tab
7. confirmed peeking card is shown with latest time stamp
8. waited for an hour and peeking card is refreshed and timestamp updated (eg. The Guardian World News)
9. clicked previous card and fresh feed is shown
10. added few publishers
11. added few channels
12. confirmed Top sources are shown along with the channels
13. clicked Following
14. waited for about two hours
15. switched to For You
16. confirmed new data refresh occurred
17. switched to Top sources and waited for 4 hours and refreshed the feed
18. confirmed new data refreshed occurred
19. switched to Publishers
20. confirmed new data refresh occurred
21. switched to Channels
22. confirmed new data refresh occurred

step 3	step 5	step 7	step 8	step 9	step 10	step 12	step 13	step 16	step 17	step 18	step 20	step 22