Fix DataTestMethod attributes, OrdinalIgnoreCase dictionary comparer, and explicit blob delimiter

[Copilot]

Addresses four review comments from #1316 where the dependency upgrade introduced subtle correctness issues.

Changes

• [DataTestMethod] restored for parameterized tests — The upgrade incorrectly replaced [DataTestMethod] with [TestMethod] on all [DataRow]-driven tests; MSTest requires [DataTestMethod] for test discovery/execution to work. Fixed across 62 tests in AzureStorageScenarioTests.cs and 1 in AzureStorageScaleTests.cs.

• StringComparer.OrdinalIgnoreCase in OrchestrationSessionManager.cs — ToDictionaryAsync was called with comparer: null (case-sensitive), inconsistent with the OrdinalIgnoreCase de-duplication applied to instance IDs earlier in the same method. Missed lookups could result from casing mismatches.

// Before
await instances.ToDictionaryAsync(o => o.State.OrchestrationInstance.InstanceId, comparer: null, cancellationToken);

// After
await instances.ToDictionaryAsync(o => o.State.OrchestrationInstance.InstanceId, comparer: StringComparer.OrdinalIgnoreCase, cancellationToken);

• Explicit delimiter in GetBlobsByHierarchyAsync — default (resolves to null) was passed as the delimiter, which changes SDK behavior vs. an explicit "/". Now uses a named argument for clarity.

// Before
.GetBlobsByHierarchyAsync(BlobTraits.Metadata, BlobStates.None, default, sanitizedInstanceId, default)

// After
.GetBlobsByHierarchyAsync(BlobTraits.Metadata, BlobStates.None, delimiter: "/", sanitizedInstanceId, default)

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