Adds logic for 90% contribution amount

[NejcZdovc]

Resolves #14319

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).
• 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. (Ask a Brave employee to help if you cannot access this document.)

Test Plan:

• enable payments
• add 90% - 99% BAT of your monthly budget to your wallet
• make sure that you don't see insufficient notification
• make contribution
• when contribution is done click on payment history icon
• make sure that you see correct amount on the history list (not monthly budget, but actual BAT)
• click on the PDF
• make sure that total is again actual BAT
• sum BAT amounts in the table and make sure that total is correct

Reviewer Checklist:

• Request a security/privacy review as needed if one was not already requested.

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[jasonrsadler]

++ Code works great 🏆

[NejcZdovc]

master 423d50d
0.23 9ed7cd1