optimize AssetsInvalidated event args

Some quick benchmarks show that...
- `new HashSet<T>(values)` (266ns) is 79% faster than `values.ToImmutableHashSet()` (1440ns);
- filling a hash set with a loop (554ns) is 21% faster than filling it from a LINQ enumerable (697ns);
- and searching a `HashSet` (18ns) is 49% faster than searching an `ImmutableHashSet` (35ns).

src/SMAPI/Events/AssetsInvalidatedEventArgs.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 
 namespace StardewModdingAPI.Events;
 
@@ -22,11 +21,16 @@ public class AssetsInvalidatedEventArgs : EventArgs
     ** Public methods
     *********/
     /// <summary>Construct an instance.</summary>
-    /// <param name="names">The asset names that were invalidated.</param>
-    /// <param name="namesWithoutLocale">The <paramref name="names"/> with any locale codes stripped.</param>
-    internal AssetsInvalidatedEventArgs(IEnumerable<IAssetName> names, IEnumerable<IAssetName> namesWithoutLocale)
+    /// <param name="assetNames">The asset names that were invalidated.</param>
+    internal AssetsInvalidatedEventArgs(ICollection<IAssetName> assetNames)
     {
-        this.Names = names.ToImmutableHashSet();
-        this.NamesWithoutLocale = namesWithoutLocale.ToImmutableHashSet();
+        HashSet<IAssetName> names = new(assetNames);
+
+        HashSet<IAssetName> namesWithoutLocale = [];
+        foreach (IAssetName name in names)
+            namesWithoutLocale.Add(name.GetBaseAssetName());
+
+        this.Names = names;
+        this.NamesWithoutLocale = namesWithoutLocale;
     }
 }

src/SMAPI/Framework/SCore.cs

@@ -1415,7 +1415,7 @@ internal class SCore : IDisposable
     private void OnAssetsInvalidated(ICollection<IAssetName> assetNames)
     {
         if (this.EventManager.AssetsInvalidated.HasListeners)
-            this.EventManager.AssetsInvalidated.Raise(new AssetsInvalidatedEventArgs(assetNames, assetNames.Select(p => p.GetBaseAssetName())));
+            this.EventManager.AssetsInvalidated.Raise(new AssetsInvalidatedEventArgs(assetNames));
     }
 
     /// <summary>Reload the SMAPI settings.</summary>