Add primitive to invalidate samples cached by a sample store

The use case for this is in client, in the editor more specifically. I'm
working on better support for custom samples, and a lack of an
invalidation primitive in `SampleStore` meant that even after a sample
was replaced, the old sample would play in the editor until the editor
is exited and re-entered.

A possible client-side alternative of recycling the entire sample store
*is* probably possible, but I think it's excessive.

osu.Framework/Audio/AudioCollectionManager.cs

@@ -28,6 +28,20 @@ namespace osu.Framework.Audio
             });
         }
 
+        public void RemoveItem(T item)
+        {
+            EnqueueAction(() =>
+            {
+                if (!Items.Contains(item)) return;
+
+                if (item is IAdjustableAudioComponent adjustable)
+                    adjustable.UnbindAdjustments(this);
+
+                Items.Remove(item);
+                ItemRemoved(item);
+            });
+        }
+
         void IBassAudio.UpdateDevice(int deviceIndex) => UpdateDevice(deviceIndex);
 
         internal virtual void UpdateDevice(int deviceIndex)

osu.Framework/Audio/Sample/ISampleStore.cs

@@ -14,5 +14,10 @@ namespace osu.Framework.Audio.Sample
         /// Add a file extension to automatically append to any lookups on this store.
         /// </summary>
         void AddExtension(string extension);
+
+        /// <summary>
+        /// Invalidates the cache for the sample with the given <paramref name="name"/>.
+        /// </summary>
+        void Invalidate(string name);
     }
 }

osu.Framework/Audio/Sample/SampleStore.cs

@@ -62,6 +62,15 @@ namespace osu.Framework.Audio.Sample
         public Task<Sample> GetAsync(string name, CancellationToken cancellationToken = default) =>
             Task.Run(() => Get(name), cancellationToken);
 
+        public void Invalidate(string name)
+        {
+            lock (factories)
+            {
+                if (factories.Remove(name, out var factory))
+                    RemoveItem(factory);
+            }
+        }
+
         protected override void UpdateState()
         {
             FrameStatistics.Add(StatisticsCounterType.Samples, factories.Count);