Add Span<T> Sort extension Methods

[alastairlundy]

Added missing Span<T> Sort extension methods that are in .NET 5+ .

Tests:

#if FeatureMemory && !NET5_0_OR_GREATER

partial class PolyfillTests
{
    [Test]
    public static void DefaultSpanSortBehaviour()
    {
        var expected = Enumerable.Range(0, 10).ToArray();
        var reversed = Enumerable.Range(0, 10)
            .Reverse().ToArray();

        Span<int> actual = reversed;

        Span<char> chars = ['d', 'c', 'b', 'a'];

        chars.Sort();

        Assert.That(expected.SequenceEqual(actual));
    }

    [Test]
    public static void Sort_Comparison_HighToLow()
    {
        var expected = Enumerable.Range(0, 10).Reverse().ToArray();
        var notReversed = Enumerable.Range(0, 10).ToArray();

        Span<int> actual = notReversed;

        actual.Sort((x, y) => x.CompareTo(y));

        Assert.That(expected.SequenceEqual(actual));
    }

    [Test]
    public static void Sort_Separate_Spans_Comparison_HighToLow()
    {
        var expectedKeys = Enumerable.Range(0, 3).Reverse().ToArray();
        var expectedItems = new[]{'a', 'b', 'c'}.AsEnumerable().Reverse().ToArray();

        var actualKeys = Enumerable.Range(0, 3).ToArray();
        var actualItems = new[]{'a', 'b', 'c'};

        Span<int> actualKeysSpan = actualKeys;

        actualKeysSpan.Sort(actualItems, (x, y) => x >= y ? 1 : -1);

        Assert.That(expectedKeys.SequenceEqual(actualKeys));
        Assert.That(expectedItems.SequenceEqual(actualItems));
    }
}
#endif

Consume:
Updated Span Methods:

#if FeatureMemory

    void Span_Methods()
    {
        var span = new Span<char>(new char[1]);
        _ = span.TrimEnd();
        _ = span.TrimStart();

        var array = Enumerable.Range(0, 5).ToArray();

#if !NET8_0_OR_GREATER
        Polyfill.Shuffle(array);
#else
        Random.Shared.Shuffle(array);
#endif

        var numbers = new Span<int>(array);
        numbers.Sort();
    }

#endif

Readme:

* `void Sort<T>(Span<T>) where T : IComparable<T>` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.memoryextensions.sort?view=net-10.0#system-memoryextensions-sort-1(system-span((-0))))
* `void Sort<T, TComparer>(Span<T>, TComparer) where TComparer : IComparer<T>` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.memoryextensions.sort?view=net-10.0#system-memoryextensions-sort-2(system-span((-0))-1)) 
* `void Sort<TKey, TValue, TComparer>(Span<TKey>, Span<TValue>, TComparer)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.memoryextensions.sort?view=net-10.0#system-memoryextensions-sort-3(system-span((-0))-system-span((-1))-2))
* `void Sort<TKey, TValue>(Span<TKey>, Span<TValue>)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.memoryextensions.sort?view=net-8.0#system-memoryextensions-sort-2(system-span((-0))-system-span((-1))))
* `void Sort<TKey, TValue>(Span<TKey>, Span<TValue>, Comparison<TKey>)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.memoryextensions.sort?view=net-10.0#system-memoryextensions-sort-2(system-span((-0))-system-span((-1))-system-comparison((-0))))

[SimonCropp]

can u update from the main line

[alastairlundy]

can u update from the main line

Done.

[SimonCropp]

seems the build failed?

[alastairlundy]

seems the build failed?
Didn't realize the Test framework/library changed. I've switched the methods to be async, return Tasks, and await Asserts.

Despite being on the latest changes from main, Rider says it can't resolve Test or Assert from TUnit and thinks there's missing NUnit references even though the project's switched to TUnit. I've tried rebuilding it with no change in errors.

Every test class gives these errors:
Error CS0246 : The type or namespace name 'TestAttribute' could not be found (are you missing a using directive or an assembly reference?)

Error CS0246 : The type or namespace name 'Test' could not be found (are you missing a using directive or an assembly reference?)

[alastairlundy]

@SimonCropp Should be fixed now. As an aside it would be nice to be able to use Ensure inside of Polyfill itself even if consuming projects don't enable it. Using it inside of Polyfill right now causes errors.

[alastairlundy]

Not sure why it's still failing on Appveyor but I'll keep looking into it.

[alastairlundy]

@SimonCropp Well now it's failing for an entirely different reason which started after most recently merging main into this branch. Consume can't find the extension method when it can sees the other Memory extension methods in Polyfill.

Was there any Memory related configuration or packaging changes in main recently?

[SimonCropp]

@alastairlundy your changes look basically good. I am going to merge this, and trouble shoot the build on my side.