Include currently active EVM version in `admin_nodeInfo` response

[matthew1001]

PR description

Adds a new field activeFork to the response body of admin_nodeInfo JSON/RPC requests.

The JSON/RPC call already returns the fork configuration but that requires the caller to make multiple calls and compare chain heights and/or timestamps to infer the currently active fork. The new field makes it possible to determine accurately in a single call.

The value is whatever getName() returns for the active ProtocolSpec. This means it is sentence cased (upper-case first letter) but a caller would be expected to use a case-insensitive string compare so I'm not inclined to upper or lower case the string.

Example output with the shanghai fork EVM enabled:

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "enode": "enode://beea7aa3a6e1f862870a456239dbf9a232d9a69e58edfeda92193f679bdbf3960bb7f41bc6f0d574c4d0c6baa2324c7279045405ef8a240906bc13d3145ccc14@127.0.0.1:30303",
        "listenAddr": "127.0.0.1:30303",
        "activeFork": "Shanghai",    <<-- NEW FIELD
        "ip": "127.0.0.1",
        "name": "besu/v24.5-develop-4753b28/osx-aarch_64/openjdk-java-17",
        "id": "beea7aa3a6e1f862870a456239dbf9a232d9a69e58edfeda92193f679bdbf3960bb7f41bc6f0d574c4d0c6baa2324c7279045405ef8a240906bc13d3145ccc14",
        "ports": {
            "discovery": 30303,
            "listener": 30303
        },
        "protocols": {
            "eth": {
                "config": {
                    "chainId": 1337,
                    "berlinBlock": 0,
                    "londonBlock": 0,
                    "shanghaiTime": 1716294470,
                    "qbft": {
                        "epochLength": 30000,
                        "blockPeriodSeconds": 2,
                        "requestTimeoutSeconds": 4
                    },
                    "zeroBaseFee": true
                },
                "difficulty": 62,
                "genesis": "0xf1b9d4b087f35660b73ef0ad56d0f241009c422459500f0a1e8f421ffbe5c29c",
                "head": "0x67ed5c441d3a2eba53c97b8f3b88ccb217ac17084ad0ed722fe894963a49ba6f",
                "network": 1337
            }
        }
    }
}

I've tested the call before and after a fork to check that the value of activeFork changes as soon as the new fork is enabled.

Fixed Issue(s)

Fixes https://github.com/hyperledger/besu/issues/7064