ethdb, rpc: support building on js/wasm (#17709)

The changes allow building WebAssembly applications which use ethclient.Client.

ethdb/database_js_test.go

@@ -0,0 +1,25 @@
+// Copyright 2014 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it 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 go-ethereum library is distributed in the hope that it 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/>.
+
+// +build js
+
+package ethdb_test
+
+import (
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+var _ ethdb.Database = &ethdb.LDBDatabase{}