core/types: fix json encoding for Request

[islishude]

The #29431 adds requests to the block type

go-ethereum/internal/ethapi/api.go

Lines 1309 to 1311 in dfd33c7

	if block.Header().RequestsHash != nil {
	fields["requests"] = block.Requests()
	}

But it doesn't have correct json encoding, the rpc always returns "requests": [{}]

[fjl]

Also fixed by #30425

[islishude]

I just checked out #30425, it uses a raw bytes for both engine api and jsonrpc.

I think it will be still useful to jsonrpc if we have a readable data.

so I just added an intermedia type for the Request, the json result has a type and data like following.

[
  {
    "type": 0,
    "data": {
      "pubkey": "0xab89324e578c5b0162f260340bf9505080dab873c5269d112f95a90b6743442b918c36c4bfeadeec840266d801966a31",
      "withdrawalCredentials": "0x01000000000000000000000005562e2e3725f641a140a098ec720f65595ae58d",
      "amount": "0x773594000",
      "signature": "0xb1921ba4029eaa2e7d783ae4f0f3417b4a0b3ef5691eb4d3a717355479ec89cb28dfac62b94815fc4939492bd00460430dafc49006a0196574741141b0acca886009d85da019039977a7cdb6c995a5691bd87914f95783c36df9f0470e6b302e",
      "index": "0x77a4190000000000"
    }
  }
]