Fix init cmd aura seal signature import (#12844)

Accommodate the genesis file format specifying aura seal, like so:
```
  "seal": {
    "authorityRound": {
      "step": 0,
      "signature": "0x00"
    }
  }
```
With this change gnosis devnets can directly be started with the `init`
command

core/genesis_write.go

@@ -439,7 +439,7 @@ func GnosisGenesisBlock() *types.Genesis {
 	return &types.Genesis{
 		Config:     params.GnosisChainConfig,
 		Timestamp:  0,
-		AuRaSeal:   common.FromHex("0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"),
+		AuRaSeal:   types.NewAuraSeal(0, common.FromHex("0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")),
 		GasLimit:   0x989680,
 		Difficulty: big.NewInt(0x20000),
 		Alloc:      readPrealloc("allocs/gnosis.json"),
@@ -450,7 +450,7 @@ func ChiadoGenesisBlock() *types.Genesis {
 	return &types.Genesis{
 		Config:     params.ChiadoChainConfig,
 		Timestamp:  0,
-		AuRaSeal:   common.FromHex("0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"),
+		AuRaSeal:   types.NewAuraSeal(0, common.FromHex("0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")),
 		GasLimit:   0x989680,
 		Difficulty: big.NewInt(0x20000),
 		Alloc:      readPrealloc("allocs/chiado.json"),
@@ -506,10 +506,12 @@ func GenesisToBlock(g *types.Genesis, tmpDir string, logger log.Logger) (*types.
 		BaseFee:       g.BaseFee,
 		BlobGasUsed:   g.BlobGasUsed,
 		ExcessBlobGas: g.ExcessBlobGas,
-		AuRaStep:      g.AuRaStep,
-		AuRaSeal:      g.AuRaSeal,
 		RequestsHash:  g.RequestsHash,
 	}
+	if g.AuRaSeal != nil && len(g.AuRaSeal.AuthorityRound.Signature) > 0 {
+		head.AuRaSeal = g.AuRaSeal.AuthorityRound.Signature
+		head.AuRaStep = uint64(g.AuRaSeal.AuthorityRound.Step)
+	}
 	if g.GasLimit == 0 {
 		head.GasLimit = params.GenesisGasLimit
 	}

core/types/genesis.go

@@ -35,6 +35,7 @@ import (
 
 //go:generate gencodec -type Genesis -field-override genesisSpecMarshaling -out gen_genesis.go
 //go:generate gencodec -type GenesisAccount -field-override genesisAccountMarshaling -out gen_genesis_account.go
+//go:generate gencodec -type AuRaSeal -out gen_aura_seal.go
 
 var ErrGenesisNoConfig = errors.New("genesis has no chain configuration")
 
@@ -51,8 +52,7 @@ type Genesis struct {
 	Coinbase   common.Address `json:"coinbase"`
 	Alloc      GenesisAlloc   `json:"alloc"      gencodec:"required"`
 
-	AuRaStep uint64 `json:"auRaStep"`
-	AuRaSeal []byte `json:"auRaSeal"`
+	AuRaSeal *AuRaSeal `json:"seal"`
 
 	// These fields are used for consensus tests. Please don't use them
 	// in actual genesis blocks.
@@ -68,6 +68,20 @@ type Genesis struct {
 	RequestsHash          *common.Hash `json:"requestsHash"`          // EIP-7685
 }
 
+type AuRaSeal struct {
+	AuthorityRound struct {
+		Step      math.HexOrDecimal64 `json:"step"`
+		Signature hexutility.Bytes    `json:"signature"`
+	} `json:"authorityRound"`
+}
+
+func NewAuraSeal(step uint64, signature []byte) *AuRaSeal {
+	a := AuRaSeal{}
+	a.AuthorityRound.Step = math.HexOrDecimal64(step)
+	a.AuthorityRound.Signature = append([]byte{}, signature...)
+	return &a
+}
+
 // GenesisAlloc specifies the initial state that is part of the genesis block.
 type GenesisAlloc map[common.Address]GenesisAccount