Refactor CameraProvider: Improve camera refresh logic and ensure proper semaphore usage

Author: zhitaop

src/CommunityToolkit.Maui.Camera/Interfaces/ICameraProvider.shared.cs

@@ -14,7 +14,7 @@ public interface ICameraProvider
 	/// List is initialized using <see cref="InitializeAsync"/>, and can be refreshed using <see cref="RefreshAvailableCameras(CancellationToken)"/>
 	/// </remarks>
 	IReadOnlyList<CameraInfo>? AvailableCameras { get; }
-	
+
 	/// <summary>
 	/// Gets a value indicating whether the camera provider has been successfully initialized.
 	/// </summary>

src/CommunityToolkit.Maui.Camera/Providers/CameraProvider.shared.cs

@@ -25,28 +25,42 @@ public void Dispose()
 		GC.SuppressFinalize(this);
 	}
 
+	Task GetRefreshTask(CancellationToken token)
+	{
+		if (refreshAvailableCamerasTask is null || refreshAvailableCamerasTask.IsCompleted)
+		{
+			refreshAvailableCamerasTask = PlatformRefreshAvailableCameras(token).AsTask();
+		}
+
+		return refreshAvailableCamerasTask;
+	}
+
 	/// <inheritdoc/>	
 	public async ValueTask InitializeAsync(CancellationToken token)
 	{
-		if (!IsInitialized)
+		await refreshAvailableCamerasSemaphore.WaitAsync(token);
+
+		try
+		{
+			if (!IsInitialized)
+			{
+				await GetRefreshTask(token);
+			}
+		}
+		finally
 		{
-			await RefreshAvailableCameras(token);
+			refreshAvailableCamerasSemaphore.Release();
 		}
 	}
 
 	/// <inheritdoc/>
 	public async Task RefreshAvailableCameras(CancellationToken token)
 	{
 		await refreshAvailableCamerasSemaphore.WaitAsync(token);
-		
+
 		try
 		{
-			if (refreshAvailableCamerasTask is null || refreshAvailableCamerasTask.IsCompleted)
-			{
-				refreshAvailableCamerasTask = PlatformRefreshAvailableCameras(token).AsTask();
-			}
-
-			await refreshAvailableCamerasTask;
+			await GetRefreshTask(token);
 		}
 		finally
 		{
@@ -64,6 +78,6 @@ void Dispose(bool disposing)
 			refreshAvailableCamerasTask = null;
 		}
 	}
-	
+
 	private partial ValueTask PlatformRefreshAvailableCameras(CancellationToken token);
 }