eth/catalyst: add catalyst API prototype (#22641)

This change adds the --catalyst flag, enabling an RPC API for eth2 integration.
In this initial version, catalyst mode also disables all peer-to-peer networking.

Co-authored-by: Mikhail Kalinin <noblesse.knight@gmail.com>
Co-authored-by: Felix Lange <fjl@twurst.com>

eth/catalyst/gen_blockparams.go

@@ -0,0 +1,46 @@
+// Code generated by github.com/fjl/gencodec. DO NOT EDIT.
+
+package catalyst
+
+import (
+	"encoding/json"
+	"errors"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+var _ = (*assembleBlockParamsMarshaling)(nil)
+
+// MarshalJSON marshals as JSON.
+func (a assembleBlockParams) MarshalJSON() ([]byte, error) {
+	type assembleBlockParams struct {
+		ParentHash common.Hash    `json:"parentHash"    gencodec:"required"`
+		Timestamp  hexutil.Uint64 `json:"timestamp"     gencodec:"required"`
+	}
+	var enc assembleBlockParams
+	enc.ParentHash = a.ParentHash
+	enc.Timestamp = hexutil.Uint64(a.Timestamp)
+	return json.Marshal(&enc)
+}
+
+// UnmarshalJSON unmarshals from JSON.
+func (a *assembleBlockParams) UnmarshalJSON(input []byte) error {
+	type assembleBlockParams struct {
+		ParentHash *common.Hash    `json:"parentHash"    gencodec:"required"`
+		Timestamp  *hexutil.Uint64 `json:"timestamp"     gencodec:"required"`
+	}
+	var dec assembleBlockParams
+	if err := json.Unmarshal(input, &dec); err != nil {
+		return err
+	}
+	if dec.ParentHash == nil {
+		return errors.New("missing required field 'parentHash' for assembleBlockParams")
+	}
+	a.ParentHash = *dec.ParentHash
+	if dec.Timestamp == nil {
+		return errors.New("missing required field 'timestamp' for assembleBlockParams")
+	}
+	a.Timestamp = uint64(*dec.Timestamp)
+	return nil
+}