Bug 1702689 - Fix browsertime_benchmark.js to collect all pagecycle results...

Bug 1702689 - Fix browsertime_benchmark.js to collect all pagecycle results r=perftest-reviewers,sparky

Fixed browsertime benchmark script to correctly run the tests, fix python code to collect all the pagecycles data and disable unity-webgl test running on windows7.

Differential Revision: https://phabricator.services.mozilla.com/D110683