Serialize a list to JSON: retarget net10.0, add stream serialization

[vladimir-pecanac-main]

Sample update for How to Serialize a List to JSON in C# (json-csharp/HowToSerializeAListToJsonInCSharp).

What changed

• Both projects retargeted net7.0 -> net10.0. net7.0 is out of support.
• Packages bumped (versions read from NuGet on the day, not from memory): BenchmarkDotNet 0.13.5 -> 0.15.8, Newtonsoft.Json 13.0.2 -> 13.0.4, Microsoft.NET.Test.Sdk 17.3.2 -> 18.9.0, xunit 2.4.2 -> 2.9.3, xunit.runner.visualstudio 2.4.5 -> 4.0.0, coverlet.collector 3.1.2 -> 10.0.1.
• New SerializeToStreamAsync(Stream) on SerializeListToJsonWithSystemTextJson, calling JsonSerializer.SerializeAsync(stream, clubList, _options), plus one test asserting the stream's contents match the expected JSON. The article gains a section on writing a list straight to a file or a stream, and this is the code behind it.
• Club.NumberOfPlayers is now an int. It was a string holding "26", so every JSON sample on the page printed "numberOfPlayers": "26" in quotes next to a bare "yearFounded": 1886 - in an article about turning C# objects into JSON. Both test expectation strings updated with it.
• Primary constructors on the two serializer classes, and Program.cs lifted to top-level statements.

Verification

• dotnet build -c Release: 0 warnings, 0 errors on SDK 10.0.302 (runtime 10.0.10).
• dotnet test -c Release: 5/5 passed (4 existing + the new stream test).
• Benchmark re-run on net10.0. The published table's row labels never matched the [Benchmark] method names, so the article's console block is being replaced with the real output:

| Method                                   | Mean     | Error     | StdDev    | Allocated |
|----------------------------------------- |---------:|----------:|----------:|----------:|
| SystemTextJsonSerializeMethod            | 3.297 ms | 0.0560 ms | 0.0496 ms |   2.23 MB |
| SystemTextJsonSerializeToUtf8BytesMethod | 3.404 ms | 0.0668 ms | 0.0769 ms |   3.35 MB |
| NewtonsoftJsonJsonSerializerClass        | 4.739 ms | 0.0716 ms | 0.0635 ms |   4.95 MB |
| NewtonsoftJsonSerializeObjectMethod      | 4.800 ms | 0.0545 ms | 0.0509 ms |   4.94 MB |

The ordering the article states still holds on .NET 10: both System.Text.Json methods finish ahead of both Newtonsoft.Json methods, and Serialize() finishes ahead of SerializeToUtf8Bytes().