Fix TUnit assertion patterns and optimize JsonObject access

[Copilot]

Addressed PR review feedback for the TUnit migration: replaced manual reference equality checks with TUnit assertions, optimized JsonObject access patterns, and corrected analyzer suppressions.

Changes

• TUnit Assertion Pattern (LocalStackProjectExtensionsTests.cs)

  • Replaced manual ReferenceEquals + exception throw with IsSameReferenceAs assertion
  • Refactored to capture builder references outside lambda to avoid async/await scope issues

• JsonObject Access Optimization (EagerLoadedServicesTests.cs)

  • Changed from ContainsKey + indexer double lookup to single indexer access with null check
  • Pattern: var value = obj["key"]; if (value is not null) { ... }

• Analyzer Suppression (LocalStackAssertions.cs)

  • Added comment explaining MA0015 suppression for property access pattern expectedLocalStack.Options
  • Analyzer flags this because it's not a direct parameter, requiring explicit suppression

• Package Version (Directory.Packages.props)

  • Verified Aspire.Hosting.AWS 9.3.0 is correct (13.1.0 doesn't exist in NuGet)

Example

Before:

if (!ReferenceEquals(result, projectBuilder))
{
    throw new InvalidOperationException("Builder should be the same reference");
}

After:

await Assert.That(resultBuilder).IsSameReferenceAs(originalBuilder);

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