The test only looked at the initial cdc_generation
generation. It made the changes bigger to go
past the raft max_command_size limit.
It then made sure this large mutation set is saved
in several raft commands.
In this commit we enhance the test to check that the
mutations are properly handled during snapshot transfer.
The problem is that the entire system.cdc_generations_v3
table is read into the topology_snapshot and it's total
size can exceed the commitlog max_record_size limit.
We need a separate injection since the compaction
could nullify the effects of the previous injection.
The test fails without the fix from the previous commit.
740b240e9d