Add gocritic linter (#1324)

* Add gocritic linter

`gocritic` provides diagnostics that check for bugs, performance, and style issues

We disable the following checks:

- commentFormatting
- captLocal
- deprecatedComment

This PR contains many `//nolint:gocritic` to disable `appendAssign`.

client/internal/engine_test.go

@@ -869,7 +869,7 @@ loop:
 		case <-ticker.C:
 			totalConnected := 0
 			for _, engine := range engines {
-				totalConnected = totalConnected + getConnectedPeers(engine)
+				totalConnected += getConnectedPeers(engine)
 			}
 			if totalConnected == expectedConnected {
 				log.Infof("total connected=%d", totalConnected)