Bring up a minimal vyconf daemon to process validation checks for set operations. This task updates the vyconf build system and makes those adjustments needed for compatibility with current vyos1x-config and vyos1x-adapter (T6717).
Update: drop hybrid set/delete functions --- the 'hybrid' period has allowed sufficient development of vyconfd to begin a full replacement of set/delete/commit/execute, continuing in T6946 and T7121.