Flaky test reporter reports severity of flakiness in Slack

Active flaky tests are reported as a list in Slack, provides a nice overview of which tests are flaky, but it's still not easy to determine how bad it is without clicking any link. It would be nice to show the severity of each test, for example failed 6/10 runs, or grade based on ratio such as low: 1-2, medium: 3-5, bad: 6-9, failed: 10

Start by tracing the existing active flaky-test Slack reporter and how it represents failed and total runs. The issue names no files or tests, so repository search is required. Done means each listed test includes its failure count or an agreed severity grade in Slack.

Written by the indexing model from the issue text.