Add check for unique chaincode names

[OsamaRab3]

This PR continues the work started in PR #528

Notes:
Original implementation credit goes to the author of PR #528
This PR finalizes and adapts their work .

TODO:
should close issue #228

[dzikowski]

I think we should approach testing in a slightly different way:

1. samples directory contains valid samples that people can use. So we should remove the newly created config
2. Instead we should test the config by altering the file on the fly. Test should throw an error for duplicate chaincode names across different channels should update the fablo config in a similar way as here: should throw an error for duplicate chaincode names across different channels
3. We can also remove should validate when all chaincode names are unique across channels, because there is no added value from it. Validation passes anyway in all cases.
4. Also we can remove e2e/fablo-config-hlf2-2orgs-2chaincodes-private-data-duplicate.yaml.test.ts and the newly created snapshot