For windows on-push signing, we'll have a need to sign windows jobs on Try and L2 trees. As such we need to make sure we bake in support for that to CoT/Signing scriptworker
This is essentially solved by bug 1366094 + in-tree changes to switch workerTypes.
Correct worker types were selected in bug 1374589. Marking this bug as a dupe of 1366094, where the major part of the work was done.