cardano-testnet | [FR] - support dijkstra genesis in testnet setup

See this comment: https://github.com/IntersectMBO/cardano-node/pull/6331/files/10b1a67b39ca3fdd45c3966defa0fbb454bd5320#r2465748692

Currently Dijkstra genesis is just written as a default instead of being copied as it is supposed to be in cardano-cli. After cardano-cli supports Dijkstra genesis generation this part of cardano-testne should be changed.