[current results] Load results data from main branch, with master as backup
[current results] Load results data from main branch, with master as backup

Once all builders have run on the main branch, the code for the master
branch can be removed.

Change-Id: I9712693a5ea6b40a81622cf8550c2383f658fa78
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/212960
Reviewed-by: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Commit-Queue: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>

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