Enable RNDT standalone shell by default (#54754)

Summary:
Pull Request resolved: #54754

Enables the standalone app shell for React Native DevTools by default.

We preserve + document this flag as an opt-out (allowing Frameworks to override this behaviour if needed).

Changelog: [Internal]

Reviewed By: motiz88

Differential Revision: D88161573

fbshipit-source-id: 64ee191dcead4e639bb3067bc9e715b1c8cdf80d

Author: huntie

packages/dev-middleware/README.md

@@ -94,7 +94,7 @@ React Native frameworks may pass an `unstable_experiments` option to `createDevM
 
 ### `unstable_experiments.enableStandaloneFuseboxShell`
 
-When `true`, the debugger frontend will launch in a standalone app shell (provided by the `@react-native/debugger-shell` package) rather than in a browser window. The standalone shell provides an improved experience and will become the default in a future version of React Native.
+Enables launching the debugger frontend in a standalone app shell (provided by the `@react-native/debugger-shell` package) rather than in a browser window. Since React Native 0.83 this defaults to `true`, and may be disabled by explicitly passing `false`.
 
 The shell is powered by a separate binary that is downloaded and cached in the background (immediately after the call to `createDevMiddleware`). If there is a problem downloading or invoking this binary for the first time, the debugger frontend will revert to launching in a browser window until the next time `createDevMiddleware` is called (typically, on the next dev server start).
 

packages/dev-middleware/src/createDevMiddleware.js

@@ -138,7 +138,7 @@ function getExperiments(config: ExperimentsConfig): Experiments {
   return {
     enableOpenDebuggerRedirect: config.enableOpenDebuggerRedirect ?? false,
     enableNetworkInspector: config.enableNetworkInspector ?? false,
-    enableStandaloneFuseboxShell: config.enableStandaloneFuseboxShell ?? false,
+    enableStandaloneFuseboxShell: config.enableStandaloneFuseboxShell ?? true,
   };
 }
 

packages/dev-middleware/src/types/Experiments.js

@@ -20,7 +20,7 @@ export type Experiments = $ReadOnly<{
   /**
    * Enables the Network panel in the debugger frontend.
    */
-  // NOTE: Used by Expo, exposing a tab labelled "Network (Expo, unstable)"
+  // NOTE: Used by Expo, exposing a tab labelled "Network (Expo)"
   enableNetworkInspector: boolean,
 
   /**