Accept --remote-debugging-port (#58905)

Summary:
Pull Request resolved: #58905

Launching the React Native DevTools shell with Electron's standard `--remote-debugging-port=<port>` switch, for example to drive it from an end-to-end test over the Chrome DevTools Protocol, opens the port but then fails to open any window. Chromium consumes the switch at startup, but the shell's own launch-argument parsing is strict and rejects it as an unknown option, so the window for `--frontendUrl` is never created and the main process logs an unhandled rejection.

Here, the launch-argument parser accepts `--remote-debugging-port` and ignores it. Chromium still acts on it, so the shell can be automated the same way as any Electron app, with no shell-specific environment variable or wrapper. Every other unknown option is still rejected.

Changelog: [Internal]

Differential Revision: D123603419

fbshipit-source-id: 8453352d1eb96b362ac07c23f491bcab12d8eb6e

Author: motiz88

packages/debugger-shell/src/electron/MainInstanceEntryPoint.js

@@ -36,6 +36,11 @@ function handleLaunchArgs(argv: string[]) {
       windowKey: {
         type: 'string',
       },
+      // Consumed by Chromium at startup (exposes the Chrome DevTools Protocol
+      // for automation); accepted here so that strict parsing doesn't reject it.
+      'remote-debugging-port': {
+        type: 'string',
+      },
     },
     args: argv,
   });