ProjectStateChangeDetector: Use HashSet for unique items

Update ProjectStateChangeDetector to use a dedicated HashSet instance to compute the most recent unique items.

Author: DustinCampbell

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/Discovery/ProjectStateChangeDetector.Comparer.cs

@@ -23,7 +23,14 @@ namespace Microsoft.VisualStudio.Razor.Discovery;
 [Export(typeof(IRazorStartupService))]
 internal partial class ProjectStateChangeDetector : IRazorStartupService, IDisposable
 {
-    private readonly record struct Work(ProjectKey Key, ProjectId? Id);
+    private readonly record struct Work(ProjectKey Key, ProjectId? Id)
+    {
+        public bool Equals(Work other)
+            => Key.Equals(other.Key);
+
+        public override int GetHashCode()
+            => Key.GetHashCode();
+    }
 
     private static readonly TimeSpan s_delay = TimeSpan.FromSeconds(1);
 
@@ -34,6 +41,7 @@ internal partial class ProjectStateChangeDetector : IRazorStartupService, IDispo
 
     private readonly CancellationTokenSource _disposeTokenSource;
     private readonly AsyncBatchingWorkQueue<Work> _workQueue;
+    private readonly HashSet<Work> _workerSet;
 
     /// <summary>
     ///  A map of assembly path strings to ProjectKeys. This will be cleared when the solution is closed.
@@ -63,6 +71,7 @@ public ProjectStateChangeDetector(
         _projectManager = projectManager;
         _options = options;
 
+        _workerSet = [];
         _disposeTokenSource = new();
         _workQueue = new AsyncBatchingWorkQueue<Work>(
             delay,
@@ -95,7 +104,9 @@ public void Dispose()
 
     private ValueTask ProcessBatchAsync(ImmutableArray<Work> items, CancellationToken token)
     {
-        foreach (var (projectKey, projectId) in items.GetMostRecentUniqueItems(Comparer.Instance))
+        _workerSet.Clear();
+
+        foreach (var (projectKey, projectId) in items.GetMostRecentUniqueItems(_workerSet))
         {
             if (token.IsCancellationRequested)
             {