[Brave News]: Miscellaneous fixes

[fallaciousreasoning]

Resolves brave/brave-browser#35001

Resolves brave/brave-browser#34975

Resolves brave/brave-browser#34973
Screencast from 2023-12-21 13-22-54.webm

Resolves brave/brave-browser#35000

Additionally:

• Fixes some console warnings (no testing needed)
• Fixes a bug where selecting Following, then For You wouldn't update the feed.

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run lint, npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

1. Select the For You feed

2. Select the Following feed

3. Select the For You feed again.
   The feed should update (to what was originally in the For You feed

4. Create a new profile

5. On the New Tab page, there should be a hint that you can scroll down to view Brave News

6. Clicking the hint should scroll down

7. It should be possible to scroll down

8. The edges of the window when viewing the opt-in card should not have a weird whiteish tint

9. Unsubscribe from all content & reload the feed

10. There should be a card showing saying we have no sources with a button to add more

11. After hiding a publisher with the ... menu the New content available. Reload? button should show up

[brave-builds]

A Storybook has been deployed to preview UI for the latest push

[brave-builds]

A Storybook has been deployed to preview UI for the latest push

[sangwoo108]

LGTM

[stephendonner]

Verification PASSED using

Brave | 1.63.61 Chromium: 120.0.6099.144 (Official Build) nightly (64-bit)
-- | --
Revision | 81091aa90eb51a34568b77533c92fd90b5017964
OS | Windows 10 Version 22H2 (Build 19045.3803)

Case 1: Peeking-card missing whilst opted-out - brave/brave-browser#35001 - PASSED

Steps:

1. installed 1.63.61
2. launched Brave
3. opened a new-tab page (alternatively, skip or complete onboarding)
4. confirmed I saw the Brave News peeking card, which is attached to the opt-in dialog
5. clicked on it / scrolled

Confirmed both clicking on and/or scrolling the Brave News peeking card works as expected

2023-12-22_01h33_45.mp4

Case 2: No sources + no content custom "Add some content..." messaging/user-prompting - brave/brave-browser#34975 - PASSED

2023-12-22_01h12_59.mp4

Case 3: No feed (source update) refresh when removing/hiding source/publisher - brave/brave-browser#34973 - PASSED

2023-12-22_01h29_59.mp4

Case 4: Initial opted-in state should automatically fetch/load new content - brave/brave-browser#35000 - PASSED

2023-12-22_01h22_24.mp4

Case 5: Following <--> For You feeds - PASSED

2023-12-22_01h26_33.mp4