[LUCI-Task-Force] Add to a luci builder's viceroy page a graph of its swarming pool utilization

For example, the "luci metrics" link on https://luci-migration.appspot.com/masters/tryserver.chromium.android/builders/android_arm64_dbg_recipe/ takes you to:
https://viceroy.corp.google.com/chrome_infra/Appengine/cr-buildbucket?duration=1w&bucket=luci.chromium.try&builder=android_arm64_dbg_recipe

It would be nice to see graphs of how its swarming pool is doing so I can determine if it needs more/less bots, but the viceroy page doesn't have that. As it is, I have to hand write a mash query:
http://shortn/_vOG08zqYMq