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.

cmd/utils/cmd.go

@@ -73,7 +73,7 @@ func StartNode(stack *node.Node) {
 		defer signal.Stop(sigc)
 		<-sigc
 		log.Info("Got interrupt, shutting down...")
-		go stack.Stop()
+		go stack.Close()
 		for i := 10; i > 0; i-- {
 			<-sigc
 			if i > 1 {