Update Network and Tracing handlers to error under multiple hosts (#54408)

Summary:
Pull Request resolved: #54408

Follows from the parent commit. This will prevent 3P CDP clients from using the `Tracing` or `Network` domains when we are in an unsupported multi React Native Host setup.

Changelog: [Internal]

Reviewed By: hoxyq

Differential Revision: D86201688

fbshipit-source-id: 052d563a371fd77c1a05ad8518e222d6bc1eb372

Author: huntie

packages/react-native/ReactCommon/jsinspector-modern/HostAgent.cpp

@@ -146,6 +146,19 @@ class HostAgent::Impl final {
     }
     if (InspectorFlags::getInstance().getNetworkInspectionEnabled()) {
       if (req.method == "Network.enable") {
+        auto& inspector = getInspectorInstance();
+        if (inspector.getSystemState().registeredPagesCount > 1) {
+          frontendChannel_(
+              cdp::jsonError(
+                  req.id,
+                  cdp::ErrorCode::InternalError,
+                  "The Network domain is unavailable when multiple React Native hosts are registered."));
+          return {
+              .isFinishedHandlingRequest = true,
+              .shouldSendOKResponse = false,
+          };
+        }
+
         sessionState_.isNetworkDomainEnabled = true;
 
         return {
@@ -386,9 +399,7 @@ class HostAgent::Impl final {
             "ReactNativeApplication.systemStateChanged",
             folly::dynamic::object("isSingleHost", isSingleHost)));
 
-    if (!isSingleHost) {
-      frontendChannel_(cdp::jsonNotification("Network.disable"));
-    }
+    frontendChannel_(cdp::jsonNotification("Network.disable"));
   }
 
  private:

packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.cpp

@@ -53,7 +53,17 @@ TracingAgent::~TracingAgent() {
 
 bool TracingAgent::handleRequest(const cdp::PreparsedRequest& req) {
   if (req.method == "Tracing.start") {
-    // @cdp Tracing.start support is experimental.
+    auto& inspector = getInspectorInstance();
+    if (inspector.getSystemState().registeredPagesCount > 1) {
+      frontendChannel_(
+          cdp::jsonError(
+              req.id,
+              cdp::ErrorCode::InternalError,
+              "The Tracing domain is unavailable when multiple React Native hosts are registered."));
+
+      return true;
+    }
+
     if (sessionState_.isDebuggerDomainEnabled) {
       frontendChannel_(
           cdp::jsonError(