node: refactor package node (#21105)

This PR significantly changes the APIs for instantiating Ethereum nodes in
a Go program. The new APIs are not backwards-compatible, but we feel that
this is made up for by the much simpler way of registering services on
node.Node. You can find more information and rationale in the design
document: https://gist.github.com/renaynay/5bec2de19fde66f4d04c535fd24f0775.

There is also a new feature in Node's Go API: it is now possible to
register arbitrary handlers on the user-facing HTTP server. In geth, this
facility is used to enable GraphQL.

There is a single minor change relevant for geth users in this PR: The
GraphQL API is no longer available separately from the JSON-RPC HTTP
server. If you want GraphQL, you need to enable it using the
./geth --http --graphql flag combination.

The --graphql.port and --graphql.addr flags are no longer available.

console/console_test.go

@@ -109,7 +109,8 @@ func newTester(t *testing.T, confOverride func(*eth.Config)) *tester {
 	if confOverride != nil {
 		confOverride(ethConf)
 	}
-	if err = stack.Register(func(ctx *node.ServiceContext) (node.Service, error) { return eth.New(ctx, ethConf) }); err != nil {
+	ethBackend, err := eth.New(stack, ethConf)
+	if err != nil {
 		t.Fatalf("failed to register Ethereum protocol: %v", err)
 	}
 	// Start the node and assemble the JavaScript console around it
@@ -135,13 +136,10 @@ func newTester(t *testing.T, confOverride func(*eth.Config)) *tester {
 		t.Fatalf("failed to create JavaScript console: %v", err)
 	}
 	// Create the final tester and return
-	var ethereum *eth.Ethereum
-	stack.Service(&ethereum)
-
 	return &tester{
 		workspace: workspace,
 		stack:     stack,
-		ethereum:  ethereum,
+		ethereum:  ethBackend,
 		console:   console,
 		input:     prompter,
 		output:    printer,