MM-52532: Fix golangci warnings (#23709)

https://mattermost.atlassian.net/browse/MM-52532

- Replace golint with revive
- Add makezero linter
- Fix all the required linter failures

Some issues in enterprise and public modules
are yet to be fixed. We send this to expediate things.

server/channels/app/email/email.go

@@ -894,7 +894,7 @@ func (es *Service) InvalidateVerifyEmailTokensForUser(userID string) *model.AppE
 		return model.NewAppError("InvalidateVerifyEmailTokensForUser", "api.user.invalidate_verify_email_tokens.error", nil, "", http.StatusInternalServerError).Wrap(err)
 	}
 
-	var appErr *model.AppError = nil
+	var appErr *model.AppError
 	for _, token := range tokens {
 		tokenExtra := struct {
 			UserId string