i18n: translate importKeepHostSettings keys

Translate the `importKeepHostSettings` and `importKeepHostSettingsDesc` keys from English placeholders into 10 locale files (ar-EG, es-ES, fa-IR, id-ID, ja-JP, pt-BR, tr-TR, vi-VN, zh-CN, zh-TW).

Also removes `main_test.go` which contained a test for a `commandHelp` function.

internal/web/translation/fa-IR.json

@@ -267,8 +267,8 @@
       "accessDirect": "DIRECT",
       "accessBlocked": "BLOCKED",
       "accessProxy": "PROXY",
-      "importKeepHostSettings": "Keep this machine's settings",
-      "importKeepHostSettingsDesc": "Keeps this panel's listen addresses, ports, base path, certificates and node identity instead of taking them from the uploaded file."
+      "importKeepHostSettings": "حفظ تنظیمات این دستگاه",
+      "importKeepHostSettingsDesc": "آدرس‌ها و پورت‌های شنود، مسیر پایه، گواهی‌ها و هویت نودِ همین پنل را نگه می‌دارد و آن‌ها را از فایل بارگذاری‌شده نمی‌گیرد."
     },
     "inbounds": {
       "totalDownUp": "دریافت/ارسال کل",