Fix user earns while native Windows and macOS notifications are suppressed

[tmancey]

Fixes brave/brave-browser#3651
Requires: #3892
Requires: #3907

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
  • 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-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:

• Confirm native Ad notifications are not shown on Windows if Focus Assist is enabled
• Confirm native Ad notifications are not shown on Windows if notifications are disabled for the user
• Confirm native Ad notifications are not shown on Windows if notifications are disabled for application
• Confirm native Ad notifications are not shown on Windows if notifications are disabled by group policy
• Confirm native Ad notifications are not shown on Windows if notifications are disabled by manifest
• Confirm native Ad notifications are not shown on macOS 10.15 if notifications set to none
• Confirm native Ad notifications are not shown on macOS 10.14 and older if notifications set to none
• Confirm ads are shown if native notifications are set to banner or alert

Note: Please test on 32-bit, 64-bit versions of Windows. Please test on all supported versions of Windows. Notifications will always be shown for Chromium Message Center (Brave fallback if native notifications are not supported)

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.

[NejcZdovc]

rewards changes looks good