Set nativeSourceCodeFetching capability in jsinspector-modern targets (#45850)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/45850

Enables the `nativeSourceCodeFetching` capability flag for the modern debugger stack on both Android and iOS. This disables source code fetching hacks within the Inspector Proxy layer and instead enables the debugger server to handle all source code fetching directly on the device.

Changelog: [Internal]

Differential Revision: D60236216

fbshipit-source-id: 1239b4d7d2233852f007114721b202d90459fa06

packages/react-native/React/Base/RCTBridge.mm

@@ -483,7 +483,7 @@ RCT_NOT_IMPLEMENTED(-(instancetype)init)
           }
           return strongSelf->_inspectorTarget->connect(std::move(remote));
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true, .nativeSourceCodeFetching = true, .prefersFuseboxFrontend = true});
   }
 
   Class bridgeClass = self.bridgeClass;

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/devsupport/inspector/InspectorNetworkHelper.java

@@ -36,7 +36,7 @@ public class InspectorNetworkHelper {
       return;
     }
 
-    // TODO(T180434718): Assign cancel function to listener
+    // TODO(T196951523): Assign cancel function to listener
     Call call = client.newCall(request);
 
     call.enqueue(

packages/react-native/ReactAndroid/src/main/jni/react/jni/ReactInstanceManagerInspectorTarget.cpp

@@ -79,7 +79,9 @@ ReactInstanceManagerInspectorTarget::ReactInstanceManagerInspectorTarget(
             -> std::unique_ptr<ILocalConnection> {
           return inspectorTarget->connect(std::move(remote));
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true,
+         .nativeSourceCodeFetching = true,
+         .prefersFuseboxFrontend = true});
   }
 }
 

packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactHostInspectorTarget.cpp

@@ -44,7 +44,9 @@ JReactHostInspectorTarget::JReactHostInspectorTarget(
           // Reject the connection.
           return nullptr;
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true,
+         .nativeSourceCodeFetching = true,
+         .prefersFuseboxFrontend = true});
   }
 }
 

packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHost.mm

@@ -227,7 +227,7 @@ class RCTHostHostTargetDelegate : public facebook::react::jsinspector_modern::Ho
           }
           return strongSelf->_inspectorTarget->connect(std::move(remote));
         },
-        {.nativePageReloads = true, .prefersFuseboxFrontend = true});
+        {.nativePageReloads = true, .nativeSourceCodeFetching = true, .prefersFuseboxFrontend = true});
   }
   if (_instance) {
     RCTLogWarn(