feat: expose additional ethapi servers (#245)

## Why this should be merged

Required for SAE to support more of the required APIs. I left out the
account and personal APIs, as we really shouldn't be managing any keys
on the node.

## How this works

Follows the same style that already existed. Additionally, copied the
upstream description for the types.

## How this was tested

Only local testing (although the prior functions were also not tested)

libevm/ethapi/ethapi.go

@@ -26,13 +26,25 @@ type (
 )
 
 type (
-	// BlockChainAPI exposes RPC methods for querying chain data.
+	// EthereumAPI provides an API to access Ethereum related information.
+	EthereumAPI = ethapi.EthereumAPI
+	// BlockChainAPI provides an API to access Ethereum blockchain data.
 	BlockChainAPI = ethapi.BlockChainAPI
-	// TransactionAPI exposes RPC methods for querying and creating
+	// TransactionAPI exposes methods for reading and creating transaction data.
-	// transactions.
 	TransactionAPI = ethapi.TransactionAPI
+	// TxPoolAPI offers and API for the transaction pool. It only operates on
+	// data that is non-confidential.
+	TxPoolAPI = ethapi.TxPoolAPI
+	// DebugAPI is the collection of Ethereum APIs exposed over the debugging
+	// namespace.
+	DebugAPI = ethapi.DebugAPI
 )
 
+// NewEthereumAPI is identical to [ethapi.NewEthereumAPI].
+func NewEthereumAPI(b Backend) *EthereumAPI {
+	return ethapi.NewEthereumAPI(b)
+}
+
 // NewBlockChainAPI is identical to [ethapi.NewBlockChainAPI].
 func NewBlockChainAPI(b Backend) *BlockChainAPI {
 	return ethapi.NewBlockChainAPI(b)
@@ -42,3 +54,13 @@ func NewBlockChainAPI(b Backend) *BlockChainAPI {
 func NewTransactionAPI(b Backend, nonceLock *AddrLocker) *TransactionAPI {
 	return ethapi.NewTransactionAPI(b, nonceLock)
 }
+
+// NewTxPoolAPI is identical to [ethapi.NewTxPoolAPI].
+func NewTxPoolAPI(b Backend) *TxPoolAPI {
+	return ethapi.NewTxPoolAPI(b)
+}
+
+// NewDebugAPI is identical to [ethapi.NewDebugAPI].
+func NewDebugAPI(b Backend) *DebugAPI {
+	return ethapi.NewDebugAPI(b)
+}