feat: partially expose internal/ethapi package (#182)

## Why this should be merged

Exposes API implementations for use by SAE.

## How this works

Type aliases and constructor propagation.

## How this was tested

N/A

libevm/ethapi/ethapi.go

@@ -0,0 +1,44 @@
+// Copyright 2025 the libevm authors.
+//
+// The libevm additions to go-ethereum are free software: you can redistribute
+// them and/or modify them under the terms of the GNU Lesser General Public License
+// as published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The libevm additions are distributed in the hope that they will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+// Package ethapi exposes the internal ethapi package.
+package ethapi
+
+import "github.com/ava-labs/libevm/internal/ethapi"
+
+// Type aliases required by constructors.
+type (
+	Backend    = ethapi.Backend
+	AddrLocker = ethapi.AddrLocker
+)
+
+type (
+	// BlockChainAPI exposes RPC methods for querying chain data.
+	BlockChainAPI = ethapi.BlockChainAPI
+	// TransactionAPI exposes RPC methods for querying and creating
+	// transactions.
+	TransactionAPI = ethapi.TransactionAPI
+)
+
+// NewBlockChainAPI is identical to [ethapi.NewBlockChainAPI].
+func NewBlockChainAPI(b Backend) *BlockChainAPI {
+	return ethapi.NewBlockChainAPI(b)
+}
+
+// NewTransactionAPI is identical to [ethapi.NewTransactionAPI].
+func NewTransactionAPI(b Backend, nonceLock *AddrLocker) *TransactionAPI {
+	return ethapi.NewTransactionAPI(b, nonceLock)
+}