Android: setting bg brave ads off. Issue #8641.

[gdregalo]

Resolves brave/brave-browser#8641

Submitter Checklist:

• [ x] Submitted a ticket for my issue if one did not already exist.
• [x ] 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
  • [x ] Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
  • Windows
• 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-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-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

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.

[gdregalo]

@brave/legacy_qa
Please test next scenarios.

Scenario 1.

1. Have the previous version of Brave installed.
2. Set Brave Bg adds to ON.
3. Update the app with the version having this PR.
   Expected result: Brave Bg adds are set to OFF.
4. Restart the app and make sure the value has not changed.

Scenario 2.

1. Have the previous version of Brave installed.
2. Set Brave Bg adds to OFF.
3. Update the app with the version having this PR.
   Expected result: Brave Bg adds are set to OFF.
4. Restart the app and make sure the value has not changed.

Scenario 3.

1. Do clean install of the app with the version having this PR.
   Expected result: Brave Bg adds are set to OFF.
2. Restart the app and make sure the value has not changed.

[SergeyZhukovsky]

++

[samartnik]

lgtm

[srirambv]

Verification passed on OnePlus 6T with Android 10

• Verified with setting enabled on 1.9.21 nightly build upgrading to 1.10.22 disables setting
• Verified with setting disabled on 1.9.21 nightly build upgrading to 1.10.22 retains the settings
• Verified setting is retained between browser launches
• Verified on clean install setting is disabled by default and is retained between relaunches