The page-issues reducer function that retrieves the severityLevels
for issues was incorrectly comparing two values in the multiple-issues
scenario.
Instead of comparing the severity of the current issue with the previous
value in the accumulator, it was comparing the current issue with the
previous issue in the original array, thus ignoring the
previous `maxSeverity` value in the accumulator.
Tests added and function refactored with more explicit variable names.
Bug: T203725
Change-Id: Ia4c15cbf0c2457d68a7381e8ed04c1a6b3ae65d1
f14d9514c6