fix .NET Framework build error + a few warnings

src/ImageSharp/Memory/Allocators/UniformUnmanagedMemoryPoolMemoryAllocator.cs

@@ -13,6 +13,8 @@ namespace SixLabors.ImageSharp.Memory
     internal sealed class UniformUnmanagedMemoryPoolMemoryAllocator : MemoryAllocator
     {
         private const int OneMegabyte = 1 << 20;
+
+        // 4 MB seemed to perform slightly better in benchmarks than 2MB or higher values:
         private const int DefaultContiguousPoolBlockSizeBytes = 4 * OneMegabyte;
         private const int DefaultNonPoolBlockSizeBytes = 32 * OneMegabyte;
         private readonly int sharedArrayPoolThresholdInBytes;

tests/ImageSharp.Tests.ProfilingSandbox/LoadResizeSaveParallelMemoryStress.cs

@@ -99,7 +99,7 @@ namespace SixLabors.ImageSharp.Tests.ProfilingSandbox
             string fileName = ss[0];
             string content = ss[1]
                 .Replace("TotalSeconds", stats.TotalSeconds.ToString(CultureInfo.InvariantCulture))
-                .Replace("EOL", Environment.NewLine, StringComparison.OrdinalIgnoreCase);
+                .Replace("EOL", Environment.NewLine);
             File.AppendAllText(fileName, content);
         }
 

tests/ImageSharp.Tests/Image/LargeImageIntegrationTests.cs

@@ -42,7 +42,6 @@ namespace SixLabors.ImageSharp.Tests
         [WithBasicTestPatternImages(width: 10, height: 10, PixelTypes.Rgba32)]
         public void TryGetSinglePixelSpan_WhenImageTooLarge_ReturnsFalse(TestImageProvider<Rgba32> provider)
         {
-
             provider.LimitAllocatorBufferCapacity().InPixels(10);
             using Image<Rgba32> image = provider.GetImage();
             Assert.False(image.TryGetSinglePixelSpan(out Span<Rgba32> imageSpan));