fix: reload network test fixtures each test to prevent shared-ref drain

Clear button mutations on httpProfile/socketProfile in FakeVmServiceWrapper
clear the underlying lists in place. Since setUpAll shared the same fixture
refs across all tests, a test that taps Clear would leave empty profiles for
the next test. Move fixture load to setUp so each test gets fresh instances.

Fixes CI failures on test_ddc and test_dart2js.

Author: ishaquehassan

packages/devtools_app/test/screens/network/network_profiler_test.dart

@@ -52,8 +52,6 @@ void main() {
   setUpAll(() {
     setGlobal(OfflineDataController, OfflineDataController());
     socketProfile = loadSocketProfile();
-    httpProfile = loadHttpProfile();
-    setGlobal(IdeTheme, IdeTheme());
     setGlobal(
       DevToolsEnvironmentParameters,
       ExternalDevToolsEnvironmentParameters(),
@@ -65,6 +63,12 @@ void main() {
 
   group('Network Profiler', () {
     setUp(() {
+      // Reload the fixtures for every test. Clearing requests mutates these
+      // shared profiles in place (FakeVmServiceWrapper clears the same lists
+      // aliased by _startingRequests/_startingSockets), so a test that taps
+      // Clear would otherwise leave them empty for the next test.
+      socketProfile = loadSocketProfile();
+      httpProfile = loadHttpProfile();
       fakeServiceConnection = FakeServiceConnectionManager(
         service: FakeServiceManager.createFakeService(
           socketProfile: socketProfile,