Make RankingUpdate detailedAssertEquals detailed

Currently, NotificationListenerServiceTest detailedAssertEquals on
NotificationRankingUpdates just does a simple assertEquals on the
ranking map references, which isn't very detailed (and doesn't actually
check for true equality; two equivalent maps that have different
references but identical entries will fail this assert.)

Instead we should be calling detailedAssertEquals on the constitutent
ranking maps instead.

Test: Test only change
Bug: 284297289
Change-Id: Iac4dc35f538a8baa6892affe5e1d3002f0a1e6ad