Terminate Tower instances after CI ends. (#37265)

* Remove obsolete Tower support from manage_ci.
* Add missing remote settings to cloud tests.

test/utils/shippable/cloud.sh

@@ -9,6 +9,9 @@ image="${args[1]}"
 python="${args[2]}"
 target="posix/ci/cloud/group${args[3]}/"
 
+stage="${S:-prod}"
+
 # shellcheck disable=SC2086
 ansible-test integration --color -v --retry-on-error "${target}" ${COVERAGE:+"$COVERAGE"} ${CHANGED:+"$CHANGED"} \
+    --remote-terminate always --remote-stage "${stage}" \
     --docker "${image}" --python "${python}" --changed-all-target "${target}smoketest/"