Support validator withdrawals (#265)

- Retrieves indexed withdrawal objects with blocks over RPC.
- Includes system-tests in CI workflow.
- Uses external fixturenet stack in CI tests.

Depends on
- cerc-io/ipld-eth-db#7
- cerc-io/plugeth-statediff#25

To induce and test validator withdrawals:
  - cerc-io/lighthouse#1
  - cerc-io/fixturenet-eth-stacks#19
  - cerc-io/system-tests#16

Reviewed-on: cerc-io/ipld-eth-server#265

cmd/root.go

@@ -95,7 +95,7 @@ func init() {
 
 func initConfig() {
 	if cfgFile == "" && envFile == "" {
-		log.Fatal("No configuration file specified, use --config , --env flag to provide configuration")
+		log.Warn("No configuration file specified, use --config , --env flag to provide configuration")
 	}
 
 	if cfgFile != "" {

cmd/serve.go

@@ -60,6 +60,7 @@ func serve() {
 		logWithCommand.Fatal(err)
 	}
 	logWithCommand.Debugf("server config: %+v", serverConfig)
+	logWithCommand.Debugf("chain config: %+v", serverConfig.ChainConfig)
 	server, err := s.NewServer(serverConfig)
 	if err != nil {
 		logWithCommand.Fatal(err)