add-chain should detect legacy rollup.json formats using "plasma"

[geoknee]

And direct the user to instructions for migrating the rollup.json.

We should add a test case for a legacy rollup.json, we can use the one from redstone as a guide:

{
  "genesis": {
    "l1": {
      "hash": "0xb9ec694afdde2e2ed661ed8ec56dace5cf8723801342fa1229e693f2a98af672",
      "number": 19578374
    },
    "l2": {
      "hash": "0xa4f55631013577464810893a05b18f07fe483885a6ef93e0060e7128bdf4ca3b",
      "number": 0
    },
    "l2_time": 1712185091,
    "system_config": {
      "batcherAddr": "0xa31cb9bc414601171d4537580f98f66c03aecd43",
      "overhead": "0x0000000000000000000000000000000000000000000000000000000000000001",
      "scalar": "0x0000000000000000000000000000000000000000000000000000000000001def",
      "gasLimit": 100000000
    }
  },
  "block_time": 2,
  "max_sequencer_drift": 600,
  "seq_window_size": 3600,
  "channel_timeout": 300,
  "l1_chain_id": 1,
  "l2_chain_id": 690,
  "regolith_time": 0,
  "canyon_time": 0,
  "delta_time": 0,
  "ecotone_time": 0,
  "batch_inbox_address": "0xff00000000000000000000000000000000000690",
  "deposit_contract_address": "0xc7bcb0e8839a28a1cfadd1cf716de9016cda51ae",
  "l1_system_config_address": "0x8f2428f7189c0d92d1c4a5358903a8c80ec6a69d",
  "protocol_versions_address": "0x0000000000000000000000000000000000000000",
  "da_challenge_address": "0x97a2da87d3439b172e6dd027220e01c9cb565b80",
  "da_challenge_window": 3600,
  "da_resolve_window": 3600,
  "use_plasma": true
}

In the current behaviour, this results in alt_da = Ethda being set in the chain config. Presumably the add-chain consistency checks fail at runtime for a config like this, so at least we would have some kind of warning that something is not right.