Add a method to return the CPU usage of a task

[marco-c]

Can be useful to identify if a failure is intermittent or not (e.g. abnormally low CPU usage).

[jmaher]

we have this data in bigquery:
SELECT * FROM moz-fx-data-taskclu-prod-8fbf.taskclusteretl.perfherder WHERE DATE(time) > "2022-01-25" and framework='job_resource_usage' and taskId='arzAwttlQAew4Xy7wy-a1g'

you can find it in suites.subtests.name and look for cpu_percent. make sure it is on suites.name mochitest.mochitest-devtools-chrome.run-tests or something that ends with run-tests.