Adds grant claim process to Rewards (0.60)

[ryanml]

Related: brave/brave-browser#1783
(0.61): #1092

4 related UI commits were cherry picked in to the 0.60 feature branch as seen here:

https://github.com/brave/brave-ui/commits/brave-core-0.60.x

The hash this PR should be pointing at is the HEAD from above, which is: 290b128ac3f607bfc9cf084417c859df1a1d3779

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:

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