Fix user facing display name for debugger-shell (#53740)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/53740

Adjusts user facing app name used by Electron, which previously used `package.json#name` and led to this leaking into unwanted parts of the UI — e.g. "[About|Hide|Quit] react-native/debugger-shell" in the macOS menu bar.

**Changes**

- Set the `productName` field in `package.json` ([docs](https://www.electronjs.org/docs/latest/api/app#appname:~:text=npm%20modules%20spec.-,You%20should%20usually%20also%20specify%20a%20productName%20field%2C%20which%20is%20your%20application%27s%20full%20capitalized%20name%2C%20and%20which%20will%20be%20preferred%20over%20name%20by%20Electron.,-app.userAgentFallback%E2%80%8B)).

**Notes**

- This **changes** the `User-Agent` header sent by the app, now of the form `"... ReactNativeDevTools/0.82.0-main-dev ..."`.

Changelog: [Internal]

Reviewed By: vzaidman

Differential Revision: D82228307

fbshipit-source-id: dd316ce5580a3ddf4138c7c3bf76aff99e4f4801