Implement basic asynchronous LUC startup without error handling

Implement basic asynchronous LUC startup without error handling

This commit adds support for LUC startup to LUCStarter. It first
creates the parallel startup groups, then sorts their names according
to PRIORITISED_LUC_TYPES and then asynchronously processes group by
group, starting all apps in a group in parallel.

The implementation does not support cancellation nor error handling
at this point.