Adds support for min visits

[NejcZdovc]

Resolves brave/brave-browser#2110

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:

plan 1:

• enable rewards
• visit couple of sites multiple times
• go to publisher db and make sure that number of visits in activity_info matches what you did

plan 2:

• enable rewards
• visit a site
• make sure that you see it in ac table
• go to ac settings and check 5 visits as min visits
• make sure that ac table is now empty
• visit this site 4 more times
• make sure that site is now visible in ac table

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

[jasonrsadler]

Trying to test "Plan 2":
Enable Rewards via panel on clean profile. Open Rewards and leave open. Open new tab and visit a site for the required amount of time. Go to Rewards tab and continue changing required visit count. Rewards starts to become sluggish and eventually non-responsive. Close the rewards tab and go back to site that was being visited. Browse the current site again for required time (or go to a new site) and open Rewards settings on new tab. Eventually becomes non-responsive again.

Does not replicate on master.

Suspect something is holding/blocking on the activity table.

[NejcZdovc]

found out that this is because of this one brave/brave-browser#2973, so this PR is blocked until that one is done

lag should be fixed now