..and remove support for when.files-changed in the test kind. It is still used
for other kinds, and that will be addressed in other bugs.
This is re-landing of this bug, now without running test-verify excessively.
MozReview-Commit-ID: GBilXAktICZ
--HG--
extra : rebase_source : 6cc9a3b5a365d74689946bfa0296f51bc08c2113
This is just one flavor of the "reftets" suite, so we need to add a distinct
scheduling component for it.
MozReview-Commit-ID: AtKuvuUCk1l
--HG--
extra : rebase_source : 3f316f0293e8d1245fc6e891bbcd044586ab6c06