Standalone helper method to return the most recent report for a health test issue

Context

#82 (comment 2035236721)

Goal

Have a method that, given a test health issue, would return the most recent report, with timestamp, for each kind of health check (slowness, flakiness, ...).

This method could then be used in triage-ops to be able to know which issue didn't receive a report in a certain amount of time.

Edited by David Dieulivol