Use switchyard submodule
We should use https://gitlab.esss.lu.se/epics-modules/vac/vac_starting_switchyard submodule.
[edit]: We should delete or archive https://gitlab.esss.lu.se/epics-modules/vac/vac_starting_switchyard.
This wrapper is relatively small and too specific to ESS, so it will be kept as a single project as decided on https://jira.esss.lu.se/browse/ICSHWI-9343.