eth: remove check for tdd reached on pos api block tags (#27799)

This change defers to the blockchain for in what circumstances to return error, instead of handling many error-cases in the api backend.

eth/api_backend.go

@@ -78,24 +78,18 @@ func (b *EthAPIBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumb
 		return b.eth.blockchain.CurrentBlock(), nil
 	}
 	if number == rpc.FinalizedBlockNumber {
-		if !b.eth.Merger().TDDReached() {
-			return nil, errors.New("'finalized' tag not supported on pre-merge network")
-		}
 		block := b.eth.blockchain.CurrentFinalBlock()
-		if block != nil {
-			return block, nil
+		if block == nil {
+			return nil, errors.New("finalized block not found")
 		}
-		return nil, errors.New("finalized block not found")
+		return block, nil
 	}
 	if number == rpc.SafeBlockNumber {
-		if !b.eth.Merger().TDDReached() {
-			return nil, errors.New("'safe' tag not supported on pre-merge network")
-		}
 		block := b.eth.blockchain.CurrentSafeBlock()
-		if block != nil {
-			return block, nil
+		if block == nil {
+			return nil, errors.New("safe block not found")
 		}
-		return nil, errors.New("safe block not found")
+		return block, nil
 	}
 	return b.eth.blockchain.GetHeaderByNumber(uint64(number)), nil
 }
@@ -136,9 +130,6 @@ func (b *EthAPIBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumbe
 		return b.eth.blockchain.GetBlock(header.Hash(), header.Number.Uint64()), nil
 	}
 	if number == rpc.FinalizedBlockNumber {
-		if !b.eth.Merger().TDDReached() {
-			return nil, errors.New("'finalized' tag not supported on pre-merge network")
-		}
 		header := b.eth.blockchain.CurrentFinalBlock()
 		if header == nil {
 			return nil, errors.New("finalized block not found")
@@ -146,9 +137,6 @@ func (b *EthAPIBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumbe
 		return b.eth.blockchain.GetBlock(header.Hash(), header.Number.Uint64()), nil
 	}
 	if number == rpc.SafeBlockNumber {
-		if !b.eth.Merger().TDDReached() {
-			return nil, errors.New("'safe' tag not supported on pre-merge network")
-		}
 		header := b.eth.blockchain.CurrentSafeBlock()
 		if header == nil {
 			return nil, errors.New("safe block not found")