IMemoryOwner for aligned memory

AlignedMemoryManager.cs

public abstract class AlignedMemoryManager : MemoryManager<byte>
{
    // Note: No finalizer; this will deliberately leak memory if never disposed.
    // https://gist.github.com/GrabYourPitchforks/8efb15abbd90bc5b128f64981766e834#implementation-notes-when-subclassing-memorymanagert
    private IntPtr _pointer;

    protected static unsafe IntPtr Allocate(nuint byteCount, nuint alignment) => (IntPtr)NativeMemory.AlignedAlloc(byteCount, alignment);

    public override unsafe Span<byte> GetSpan() => new((void*)_pointer, ByteCount);

    public override unsafe MemoryHandle Pin(int elementIndex = 0) => new((byte*)_pointer + elementIndex);

    public override void Unpin() { }

    protected AlignedMemoryManager(IntPtr pointer) => _pointer = pointer;

    protected abstract int ByteCount { get; }

    protected override unsafe void Dispose(bool disposing)
    {
        var localHandle = Interlocked.Exchange(ref _pointer, IntPtr.Zero);
        NativeMemory.AlignedFree((void*)localHandle);
    }
}

SystemPageSizeAlignedMemoryManager.cs

public sealed class SystemPageSizeAlignedMemoryManager : AlignedMemoryManager
{
    public IMemoryOwner<byte> Allocate() => new SystemPageSizeAlignedMemoryManager();

    public SystemPageSizeAlignedMemoryManager()
        : base(AlignedMemoryManager.Allocate((nuint)Environment.SystemPageSize, (nuint)Environment.SystemPageSize))
    {
    }

    protected override int ByteCount => Environment.SystemPageSize;
}