.NET: Increase credential timeout for Integration Tests (#4472)

* Increase credential timeout for Integration Tests

* Fix format error.

* Update further tests

* Fix comment

* Rename credentials file and class.

* Fix broken reference.

dotnet/src/Shared/IntegrationTestsAzureCredentials/README.md

@@ -0,0 +1,9 @@
+# Integration Tests Azure Credentials
+
+Adds a helper for loading Azure credentials in integration tests.
+
+```xml
+<PropertyGroup>
+  <InjectSharedIntegrationTestAzureCredentialsCode>true</InjectSharedIntegrationTestAzureCredentialsCode>
+</PropertyGroup>
+```

dotnet/src/Shared/IntegrationTestsAzureCredentials/TestAzureCliCredentials.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+#pragma warning disable IDE0005 // This is required in some projects and not in others.
+using System;
+#pragma warning restore IDE0005
+using Azure.Identity;
+
+namespace Shared.IntegrationTests;
+
+/// <summary>
+/// Provides credential instances for integration tests with
+/// increased timeouts to avoid CI pipeline authentication failures.
+/// </summary>
+internal static class TestAzureCliCredentials
+{
+    /// <summary>
+    /// The default timeout for Azure CLI credential operations.
+    /// Increased from the default (~13s) to accommodate CI pipeline latency.
+    /// </summary>
+    private static readonly TimeSpan s_processTimeout = TimeSpan.FromSeconds(60);
+
+    /// <summary>
+    /// Creates a new <see cref="AzureCliCredential"/> with an increased process timeout
+    /// suitable for CI environments.
+    /// </summary>
+    public static AzureCliCredential CreateAzureCliCredential() =>
+        new(new AzureCliCredentialOptions { ProcessTimeout = s_processTimeout });
+}