Pre-duplicate kernel values in ResizeKernelMap for faster FMA convolution

[antonfirsov]

As @saucecontrol pointed out in his comment, we can get rid of VPERMS in the following code:

ImageSharp/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeKernel.cs

Lines 104 to 112 in e2211c3

	result256_0 = Fma.MultiplyAdd(
	Unsafe.As<Vector4, Vector256<float>>(ref rowStartRef),
	Avx2.PermuteVar8x32(Vector256.CreateScalarUnsafe(*(double*)bufferStart).AsSingle(), mask),
	result256_0);
	result256_1 = Fma.MultiplyAdd(
	Unsafe.As<Vector4, Vector256<float>>(ref Unsafe.Add(ref rowStartRef, 2)),
	Avx2.PermuteVar8x32(Vector256.CreateScalarUnsafe(*(double*)(bufferStart + 2)).AsSingle(), mask),
	result256_1);

If FMA is detected we should allocate 4x buffer and to the duplication in ResizeKernelMap.Calculate, which should be much cheaper than doing it in every convolution:

ImageSharp/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeKernelMap.cs

Lines 115 to 120 in e2211c3

	public static ResizeKernelMap Calculate<TResampler>(
	in TResampler sampler,
	int destinationSize,
	int sourceSize,
	MemoryAllocator memoryAllocator)
	where TResampler : struct, IResampler