[results feed] Change default view to "active failures"
[results feed] Change default view to "active failures"

The URL query fragment now shows "showLatestFailures=false" for the
"all results" view, and nothing for the "active failures" view.
Previous URL fragments remain valid, and "showLatestFailures=true" is
ignored.

Change-Id: Ibd2c55cc94721b89b9befc557f582298148e55a9
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/149180
Reviewed-by: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>

dart-lang/dart_ci,dart-lang/dart_ci,dart-lang/dart_ci,dart-lang/dart_ci