Bug 1535132: Add worker types for running instrumented builds; r=dustin

This adds worker-type alias that has dedicated workers at level-3 for running
instrumented builds, but uses a test worker type at other levels.

Differential Revision: https://phabricator.services.mozilla.com/D23576

--HG--
extra : moz-landing-system : lando

taskcluster/ci/config.yml

@@ -301,6 +301,22 @@ workers:
             implementation: generic-worker
             os: macosx
             worker-type: 'gecko-{alias}'
+        t-linux-xlarge-pgo:
+            provisioner: aws-provisioner-v1
+            implementation: docker-worker
+            os: linux
+            worker-type:
+                by-level:
+                    '3': 'gecko-{level}-t-linux-xlarge'
+                    default: 'gecko-t-linux-xlarge'
+        t-osx-1010-pgo:
+            provisioner: releng-hardware
+            implementation: generic-worker
+            os: macosx
+            worker-type:
+                by-level:
+                    '3': 'gecko-{level}-t-osx-1010'
+                    default: 'gecko-t-osx-1010'
         t-win10-64(|-gpu):
             provisioner: aws-provisioner-v1
             implementation: generic-worker