Fix O(n²) per-node UID lookup in TestNodeUidListFilter re-run path

[Copilot]

BFSTestNodeVisitor was performing an O(n) Any() linear scan over TestNodeUidListFilter.TestNodeUids for every test node visited, resulting in O(n×m) total work (n = test nodes, m = filter UIDs). This is hit on every retry/re-run via RetryExecutionFilterFactory.

Changes

• BFSTestNodeVisitor.VisitAsync: Precompute a HashSet<PlatformTestNodeUid> from TestNodeUidListFilter.TestNodeUids once before the BFS loop; replace Any() with HashSet.Contains() for O(1) per-node lookup. Adds a using alias to disambiguate from the framework-internal TestNodeUid type.
• TestingPlatformExplorer/TestingFramework.cs (sample): Same fix — extract the HashSet outside the foreach and use Contains instead of Any.

// Before: O(m) scan per node, O(n×m) total
|| listFilter.TestNodeUids.Any(uid => currentNode.StableUid.ToPlatformTestNodeUid() == uid)

// After: O(1) per node, O(n+m) total
HashSet<PlatformTestNodeUid>? uidFilterSet = _testExecutionFilter is TestNodeUidListFilter listFilter
    ? [.. listFilter.TestNodeUids]
    : null;
// ...
|| uidFilterSet.Contains(currentNode.StableUid.ToPlatformTestNodeUid())

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[Copilot]

Pull request overview

Optimizes test-node UID filtering during traversal/execution to avoid repeated linear scans when re-running/retrying tests via TestNodeUidListFilter, reducing total work from O(n×m) to ~O(n+m).

Changes:

• Precomputes a HashSet of filtered UIDs once and uses Contains for O(1) per-node membership checks in BFSTestNodeVisitor.VisitAsync.
• Applies the same pattern in the TestingPlatformExplorer sample execution loop.

Show a summary per file

File	Description
src/Adapter/MSTest.Engine/Engine/BFSTestNodeVisitor.cs	Builds a UID HashSet once and replaces per-node Any() scans with Contains().
samples/public/TestingPlatformExamples/TestingPlatformExplorer/TestingFramework/TestingFramework.cs	Uses a precomputed UID HashSet for faster filtering in the sample runner loop.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 2

[Copilot]

currentNode.StableUid is already Microsoft.Testing.Platform.Extensions.Messages.TestNodeUid, so calling ToPlatformTestNodeUid() here allocates a new TestNodeUid per visited node. If you want this to be allocation-free (and likely drop the PlatformTestNodeUid alias), you can check uidFilterSet.Contains(currentNode.StableUid) directly.

[Copilot]

In this sample, uidFilterSet is a HashSet<TestNodeUid> but Contains is called with an interpolated string, which relies on the implicit string -> TestNodeUid conversion and allocates a new TestNodeUid per check. If you want this to be allocation-free, consider storing uid.Value in a HashSet<string> (e.g., with StringComparer.Ordinal) and comparing against the computed UID string.