vinyl: generate VY_LOG_NEW_INDEX event in vy_recovery_load_index()

Currently, vy_recovery_load_index() only calls the callback for
VY_LOG_INSERT_RANGE and VY_LOG_INSERT_RUN types of records, but not
for VY_LOG_NEW_INDEX, because the latter is not needed during index
recovery. However, we will need this event for vinyl metadata log
rotation, so let's make vy_recovery_load_index() call the callback
for this type of record too.