feat: add security warnings to sandboxed renderers (#14869)

Also refactor not to use the remote module.

lib/browser/rpc-server.js

@@ -475,3 +475,11 @@ ipcMain.on('ELECTRON_BROWSER_SANDBOX_LOAD', function (event) {
     }
   }
 })
+
+ipcMain.on('ELECTRON_BROWSER_GET_LAST_WEB_PREFERENCES', function (event) {
+  try {
+    event.returnValue = [null, event.sender.getLastWebPreferences()]
+  } catch (error) {
+    event.returnValue = [errorUtils.serialize(error)]
+  }
+})