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/geth/dao_test.go

@@ -119,8 +119,7 @@ func testDAOForkBlockNewChain(t *testing.T, test int, genesis string, expectBloc
 	} else {
 		// Force chain initialization
 		args := []string{"--port", "0", "--maxpeers", "0", "--nodiscover", "--nat", "none", "--ipcdisable", "--datadir", datadir}
-		geth := runGeth(t, append(args, []string{"--exec", "2+2", "console"}...)...)
-		geth.WaitExit()
+		runGeth(t, append(args, []string{"--exec", "2+2", "console"}...)...).WaitExit()
 	}
 	// Retrieve the DAO config flag from the database
 	path := filepath.Join(datadir, "geth", "chaindata")