Monthly tips are now shown in Rewards panel summary.

[jasonrsadler]

Fixes brave/brave-browser#3177

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
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• 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

Test Plan:

1. Start Brave clean profile with reconcile-interval=10 (or lower if faster) and enable rewards.
2. Create a recurring monthly donation to a verified publisher.
3. optionally visit sites to populate autocontribute table.
4. optionally make one time tip to verified publisher.
5. When reconcilation has occurred, make sure Monthly Tips is displayed in Rewards panel summary

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