show count of pending tasks for a specific worker type in more places

[bhearsum]

A common thing for me to do when a task is pending for a period of time is to check out the count of pending tasks for that worker type. The flow for this currently is to start with the Task page, then click on the Task Queue ID link, then on the worker pool(?) link. That page shows the number of pending tasks -- but for some worker pools this list is quite long, and contains many similar named worker types, making it a bit difficult to read at times. (The best is usually to copy/paste the worker type and search for it in the page - but that's something I think to do before I click through it in most cases.)

There's at least a couple of additional places it would be helpful to show the pending count to make it easier to answer this question:

• On the specific worker type page (eg: https://firefox-ci-tc.services.mozilla.com/provisioners/gecko-t/worker-types/win10-64-2004?sortBy=Last%20Active&sortDirection=desc)
• On the Task page itself - perhaps right beside the PENDING label

[lotas]

Great suggestion, thanks Ben.
I think this will come along good with the #2939 that will give more visibility to what's inside the queue.