Add setting options to toggle NTP widgets

[imptrx]

Spec: brave/brave-browser#4510 (Current scope of this PR does not include right clicking on the widgets to open up a mini-menu)
Brave-ui Sister PR: brave/brave-ui#503
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Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Android
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• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
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• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone
• Public documentation has been updated as necessary. 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-Protection-Mode
  • 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-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

1. Open new tabs page with a fresh profile - all NTP elements should appear
2. Open settings menu from the settings icon - 3 new settings should exist below show background
3. Toggle the three options; show clock; show stats; show top sites - they should disappear/reappear on the page
4. Settings should persist after browser is closed and reopened

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

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.

[bsclifton]

@imptrx is there an issue captured that this PR fixes?
nevermind! just saw it: brave/brave-browser#4510

[cezaraugusto]

LGTM. I'm adding @petemill as reviewer who suggested moving stored data to be in settings instead of using localStorage. I'm ok either doing that as a follow-up or holding this one a bit until we have the proper api exposed

[petemill]

@cezaraugusto I'm going to PR the change to either this, or to master if this is merged first. I'm happy with either scenario but if this is merged first, any users who change the setting will have their setting reset back to default once the prefstore change lands

[petemill]

Pushed a rebase on master. We'll still want to update brave-ui sha with the result of merging brave/brave-ui#503 when that happens

[petemill]

Here's a branch which adds these remaining toggles to the pref store, for integrating perhaps by @imptrx when #2831 is merged to master and this is rebased. The branch is a rebase of this PR on that, and then adds the prefs.
https://github.com/brave/brave-core/compare/toggle-on-profile-prefs

[cezaraugusto]

set PR as blocked until #2831 is resolved

[cezaraugusto]

++ great Peter work here! thanks team this is super cool. 💯

[bsclifton]

Works great! 😄 Thanks @petemill for the example code RE: preferences. Awesome job, @imptrx!

Besides the code looking good and verifying that it works, I also verified that the new settings are persisted in the Default\Preferences file as expected 👍

[bsclifton]

Don't forget to add a test plan and link to it from brave/brave-browser#4510