Optimize HttpDateParser.TryStringToDate - #34860

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;
using System.Net.Http;

[MemoryDiagnoser]
public class Program
{
    static void Main(string[] args) => BenchmarkSwitcher.FromAssemblies(new[] { typeof(Program).Assembly }).Run(args);

    [Benchmark]
    public DateTimeOffset? DatePreferred()
    {
        var m = new HttpResponseMessage();
        m.Headers.TryAddWithoutValidation("Date", "Sun, 06 Nov 1994 08:49:37 GMT");
        return m.Headers.Date;
    }

    [Benchmark]
    public DateTimeOffset? DateAsctime()
    {
        var m = new HttpResponseMessage();
        m.Headers.TryAddWithoutValidation("Date", "Sun Nov  6 08:49:37 1994");
        return m.Headers.Date;
    }
}