Brave News V2 Cards Performance

[fallaciousreasoning]

Using styled components, any property which is unique per component will probably have poor performance, as styled-components generates and attaches a unique stylesheet for each one.

I'm pretty sure this is what's causing our poor first open performance.

[kjozwiak]

Going to be hard to QA as per brave/brave-core#15611 (comment) but we should just do a quick spot check and ensure that performance hasn't regressed. Might be hard to prove that performance has improved in a scientific way, but at least we can make sure things don't appear worse/slower 👍

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.47.126 Chromium: 108.0.5359.99 (Official Build) beta (64-bit)
-- | --
Revision | 410951fc34bb4b2cbf182231f9f779efaafaf682-refs/branch-heads/5359_71@{#9}
OS | Windows 10 Version 21H2 (Build 19044.2251)

Steps:

1. installed each respective (pre- and post-fix) build
2. launched Brave
3. opened brave://flags
4. toggled brave://flags/#brave-news-v2 to Enabled
5. clicked Relaunch
6. open a new-tab page
7. click on Customize
8. get a stopwatch started
9. click on Turn on Brave News at the 2-seconds mark
10. click to stop the stopwatch once the Customize dashboard's dialog is fully rendered

Actual: The release channel 1.46.140 took 2.56 secs to 1st time open the Brave news page whereas 1.47.123 took 1.52 secs to open the brave news, confirmed that the performance got increased in 1.47.x

1.46.140	1.47.123