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`.

management/server/metrics/selfhosted.go

@@ -200,14 +200,14 @@ func (w *Worker) generateProperties() properties {
 			expirationEnabled++
 		}
 
-		groups = groups + len(account.Groups)
-		routes = routes + len(account.Routes)
+		groups += len(account.Groups)
+		routes += len(account.Routes)
 		for _, route := range account.Routes {
 			if len(route.PeerGroups) > 0 {
 				routesWithRGGroups++
 			}
 		}
-		nameservers = nameservers + len(account.NameServerGroups)
+		nameservers += len(account.NameServerGroups)
 
 		for _, policy := range account.Policies {
 			for _, rule := range policy.Rules {
@@ -231,10 +231,10 @@ func (w *Worker) generateProperties() properties {
 		}
 
 		for _, key := range account.SetupKeys {
-			setupKeysUsage = setupKeysUsage + key.UsedTimes
+			setupKeysUsage += key.UsedTimes
 			if key.Ephemeral {
 				ephemeralPeersSKs++
-				ephemeralPeersSKUsage = ephemeralPeersSKUsage + key.UsedTimes
+				ephemeralPeersSKUsage += key.UsedTimes
 			}
 		}