[Brave News] The Brave News V2 page should be updated to match new design specs

[fallaciousreasoning]

After some discussion with the designers, we've worked out a more consistent design for the home page:

1. Popular sources should appear first
2. Suggestions should appear second
3. Channels should appear third
4. All channels should be visible
5. Popular/Suggestions should appear in a Carousel, with a view all link taking you to a full page view
6. We should remove the All Sources section

[kjozwiak]

The above will require 1.46.100 or higher for 1.46.x verification 👍

[stephendonner]

Verification PASSED using

Brave	1.46.100 Chromium: 107.0.5304.91 (Official build) dev (x86_64)
Revision	3d5948960d62418160796d5831a4d2d7d6c90fa8-refs/branch-heads/5304@{#1097}
OS	macOS Version 11.7.1 (Build 20G918)

Steps:

1. launched Brave
2. clicked on Skip welcome tour
3. opened brave://flags
4. set brave://flags/#brave-news-v2 to Enabled
5. clicked Relaunch
6. opened a new-tab page
7. clicked on Customize
8. clicked on Brave News
9. clicked on Turn on Brave News
10. checked the Customize Brave News dialog

Confirmed the following changes:

• Popular sources appeared first
• Suggestions appeared second (after following a few sources, then returning to this dialog)
• Channels appeared third
• All channels were visible (no Show more button)
• Popular & Suggestions appeared in a carousel, with a View All link taking me to a full page view
• removed previous Sources section

order of appearance	all channels visible	carousel