Cardano Updates

"diffusionMode" can be either `"InitiatorOnly"` or
`"InitiatorAndResponder"`.  If not given, the latter is the default
- for backward compatibility.  When "InitiatorOnly" is used, the
connections to these local roots will only negotiate `InitiatorOnly`
mode (it won't be possible to be reused by the other side) and will not
bind to the server address, e.g. it will be made from an ephemeral port.
See https://github.com/IntersectMBO/ouroboros-network/issues/5020 why
this feature was requested by some SPOs.

An example configuration:
```json
{ "localRoots":
    [ { "accessPoints":
          [ { "address": "10.0.0.1"
            , "port": 3001
            }
          ]
      , "advertise": false
      , "diffusionMode": "InitiatorOnly"
      , "warmValency": 1
      , "hotValency": 1
      }
    , { "accessPoints":
          [ { "address": "10.0.0.2"
            , "port": 3001
            }
          ]
      , "advertise": true
      , "diffusionMode": "InititiatorAndResponder"
      , "warmValency": 1
      , "hotValency": 1
      }
    ]
, "publicRoots": []
, "useLedgerAfterSlot": -1
}
```

"diffusionMode" can be either `"InitiatorOnly"` or
`"InitiatorAndResponder"`.  If not given, the latter is the default
- for backward compatibility.  When "InitiatorOnly" is used, the
connections to these local roots will only negotiate `InitiatorOnly`
mode (it won't be possible to be reused by the other side) and will not
bind to the server address, e.g. it will be made from an ephemeral port.
See https://github.com/IntersectMBO/ouroboros-network/issues/5020 why
this feature was requested by some SPOs.

An example configuration:
```json
{ "localRoots":
    [ { "accessPoints":
          [ { "address": "10.0.0.1"
            , "port": 3001
            }
          ]
      , "advertise": false
      , "diffusionMode": "InitiatorOnly"
      , "warmValency": 1
      , "hotValency": 1
      }
    , { "accessPoints":
          [ { "address": "10.0.0.2"
            , "port": 3001
            }
          ]
      , "advertise": true
      , "diffusionMode": "InititiatorAndResponder"
      , "warmValency": 1
      , "hotValency": 1
      }
    ]
, "publicRoots": []
, "useLedgerAfterSlot": -1
}
```

The ConsensusMode configuration option determines whether support for
Genesis syncing is enabled. If this flag is GenesisMode, alternate
targets for active peers (non- big ledger) and all big ledger targets
is used by the peer selection and churn governors in the diffusion
layer. These targets are in effect when ledger state is deemed
`TooOld` by consensus layer. The large active big ledger peer targets
crucially depend on chain skipping to maintain performance
requirements. Otherwise, in PraosMode, the legacy algorithm with
a single set of targets is employed.

This change introduces support for big ledger peers in the node.
A new optional entry in network topology JSON parser is added that is intended
to point to a path containing a serialized snapshot of big ledger peers
taken from some slot a priori. When present, this file is decoded
at node startup, or when a SIGHUP is triggered, and made available
to the diffusion layer via reading from a TVar.

Missing updating Node Configuration parser to read genesis targets and
ledger snapshot.