Add shields settings

[alexsafe]

Resolves brave/brave-browser#16300
Resolves brave/brave-browser#16299

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• 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, npm run lint, 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. Check ad blocker, fingerprinting, cookies settings as the code has been refactored
2. Check there is no conflict between shields settings and the global settings
3. Check that shields settings are working on the loaded site after swiping out and re-starting the app
4. Check for update too, as we had that issue before

[SergeyZhukovsky]

++

[srirambv]

Verification passed on OnePlus 6T with Android 10 running 1.28.51 x64 nightly build

• Verified Ads/Trackers setting is changed to allow selection between strict/standard/allow all similar to desktop
• Verified setting global setting for ad blocker to strict sets is on site shields settings as well
• Verified shields settings is visible on both normal and private tabs
• Verified shields settings shows new option after upgrade
• Verified setting ad blocker to strict and upgrading retains the setting and sets ad blocking to strict even on site shields settings