Fix custom port listening configuration through metro.config.js (#44957)

Summary:
After updating my project to 0.73.2 I noticed that even though I had a specific port set in my `metro.config.js`, every time I'd start my project, it was running on port 8081. Passing the `--port` argument would allow me to change the port, but the config from metro did not.  I checked if the metro config was being properly applied, using `--verbose` and it was.

So I dug a bit, trying to figure out what had changed and noticed the coalescing of the value, whenever the argument `--port` is not present. That seemed odd since it meant that there's always a port defined for the `options` of `loadMetroConfig`, which would always be used in the `loadConfig` step.

To confirm I was on the right track I went to the [cli-plugin-metro](https://github.com/react-native-community/cli/blob/v11.3.10/packages/cli-plugin-metro) repo, to the last release before the move here, and noticed that there was [no coalescing in the same method](https://github.com/react-native-community/cli/blob/v11.3.10/packages/cli-plugin-metro/src/commands/start/runServer.ts#L60).

In this PR, I remove the coalescing of the port from `runServer.js` from the `community-cli-plugin`, to allow the port configuration through `metro.config.js`.

## Changelog:
[INTERNAL] [FIXED] - Fix server port configuration via `metro.config.js`
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Pull Request resolved: https://github.com/facebook/react-native/pull/44957

Test Plan:
Running `yarn start` and verifying that:
- it would listen to port `8081` if no argument nor a custom port was set in `metro.config.js`
- it would listen to port `8082` if that one was defined in `metro.config.js`
- it would listend to port `8083` if that port was passed as an argument to the command (i.e. `yarn start --port 8083` even though port 8082 was defined in `metro.config.js`

Reviewed By: cortinico

Differential Revision: D58605152

Pulled By: robhogan

fbshipit-source-id: 9cf7a8b6a0d9de3af1ca4092906b4c648acee373

packages/community-cli-plugin/src/commands/start/runServer.js

@@ -57,7 +57,7 @@ async function runServer(
   const metroConfig = await loadMetroConfig(ctx, {
     config: args.config,
     maxWorkers: args.maxWorkers,
-    port: args.port ?? 8081,
+    port: args.port,
     resetCache: args.resetCache,
     watchFolders: args.watchFolders,
     projectRoot: args.projectRoot,