enhance(admin): show impersonation banner and keep password change with the user (#38924)

Follow-up to https://github.com/go-gitea/gitea/pull/38614

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

options/locale/locale_en-US.json

@@ -3052,6 +3052,8 @@
   "admin.users.new_success": "The user account \"%s\" has been created.",
   "admin.users.edit": "Edit",
   "admin.users.impersonate": "Impersonate",
+  "admin.users.impersonate_stop": "Stop impersonating",
+  "admin.users.impersonating_notice": "You are impersonating <strong>%s</strong>. Actions you take are performed as this user.",
   "admin.users.auth_source": "Authentication Source",
   "admin.users.local": "Local",
   "admin.users.auth_login_name": "Authentication Sign-In Name",