op-migrate: various sanity checks + cleanup

Adds cleanup to the migration script, ensures that
config is sane.

We cannot allow for non monotonic block time. We also
try to make eip 1159 stable at start and use a hardcoded
initial base fee.

Add additional logging

op-chain-ops/genesis/db_migration.go

@@ -120,6 +120,9 @@ func MigrateDB(ldb ethdb.Database, config *DeployConfig, l1Block *types.Block, m
 	}
 	log.Info("Completed ERC20 ETH migration", "root", newRoot)
 
+	// Set the amount of gas used so that EIP 1559 starts off stable
+	gasUsed := (uint64)(config.L2GenesisBlockGasLimit) * config.EIP1559Elasticity
+
 	// Create the bedrock transition block
 	bedrockHeader := &types.Header{
 		ParentHash:  header.Hash(),
@@ -132,16 +135,25 @@ func MigrateDB(ldb ethdb.Database, config *DeployConfig, l1Block *types.Block, m
 		Difficulty:  common.Big0,
 		Number:      new(big.Int).Add(header.Number, common.Big1),
 		GasLimit:    (uint64)(config.L2GenesisBlockGasLimit),
-		GasUsed:     0,
+		GasUsed:     gasUsed,
 		Time:        uint64(config.L2OutputOracleStartingTimestamp),
 		Extra:       bedrockTransitionBlockExtraData,
 		MixDigest:   common.Hash{},
 		Nonce:       types.BlockNonce{},
-		BaseFee:     (*big.Int)(config.L2GenesisBlockBaseFeePerGas),
+		BaseFee:     big.NewInt(params.InitialBaseFee),
 	}
 
 	bedrockBlock := types.NewBlock(bedrockHeader, nil, nil, nil, trie.NewStackTrie(nil))
 
+	log.Info(
+		"Built Bedrock transition",
+		"hash", bedrockBlock.Hash(),
+		"root", bedrockBlock.Root(),
+		"number", bedrockBlock.NumberU64(),
+		"gas-used", bedrockBlock.GasUsed(),
+		"gas-limit", bedrockBlock.GasLimit(),
+	)
+
 	res := &MigrationResult{
 		TransitionHeight:    bedrockBlock.NumberU64(),
 		TransitionTimestamp: bedrockBlock.Time(),
@@ -183,6 +195,12 @@ func MigrateDB(ldb ethdb.Database, config *DeployConfig, l1Block *types.Block, m
 	}
 	rawdb.WriteChainConfig(ldb, genesisHash, cfg)
 
+	log.Info(
+		"wrote chain config",
+		"1559-denominator", config.EIP1559Denominator,
+		"1559-elasticity", config.EIP1559Elasticity,
+	)
+
 	log.Info(
 		"wrote Bedrock transition block",
 		"height", bedrockHeader.Number,