Add basic metrics to the indexer package. (#7250)

This follows the same model as we did in the p2p package.

Rework the indexer service constructor to take a struct of arguments,
that makes it easier to construct the optional settings.
Deprecate but do not remove the existing constructor.

Clean up node initialization a little bit.

node/node_test.go

@@ -558,7 +558,8 @@ func TestNodeSetEventSink(t *testing.T) {
 		require.NoError(t, err)
 
 		indexService, eventSinks, err := createAndStartIndexerService(cfg,
-			config.DefaultDBProvider, eventBus, logger, genDoc.ChainID)
+			config.DefaultDBProvider, eventBus, logger, genDoc.ChainID,
+			indexer.NopMetrics())
 		require.NoError(t, err)
 		t.Cleanup(func() { require.NoError(t, indexService.Stop()) })
 		return eventSinks