After moving the creation of uuid out of
make_new_generation_description, this function only calls the
topology_description_generator's constructor and its generate
method. We could remove this function, but we instead simplify
the code by removing the topology_description_generator class.
We can do this refactor because make_new_generation_description
is the only place using it. We inline its generate method into
make_new_generation_description and turn its private methods into
static functions.
fab066cffe