Add mock block zero data to Test Generator.

In general we would like to replace test generator in this project with a more out of the box solution and most importantly automated one in the future however for the moment it's there.

As part of: https://github.com/cardano-foundation/cardano-rosetta-java/pull/412/files

We had to make a hack that to change genesis block from -1 to 0:
```sql
UPDATE block SET number = 0 WHERE number = -1;
UPDATE transaction SET block = 0 WHERE block_hash = 'Genesis';
```

This ticket is about fixing it properly and generating a fake block 0 with a couple of "genesis transactions".

This limitation comes from the fact that nobody is starting anymore from zero within Conway other than yaci-dev-kit.

We would see this issue if now from latest node somebody starts a new test-net then we would be missing block 0.