Refactor to support extension members

[oliverbooth]

As of C# 14.0, "extension everything" finally started to make its way into the language with the introduction of "extension members". This new construct allows the creation of extension properties and indexers, as well as static methods, properties, and indexers for a type.

For example, a static extension method might look like the following:

string result = string.Random(42);

static class Extensions
{
    extension (string)
    {
        public static string Random(int length) => new(Enumerable.Range(0, length).Select(_ => "abcdefghijklmnopqrstuvwxyz"[System.Random.Shared.Next(26)]).ToArray());
    }
}

This construct will be added to X10D in upcoming updates to add support for extension properties where appropriate, and static extension methods such as the above.

The language proposal for this feature can be found at https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/extensions

For implementation information, see: https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/extension-methods

[oliverbooth]

Upon investigation, it appears that extension blocks are binary-compatible with the current form of extension methods (which use a this parameter modifier), this should drastically reduce development time.

[oliverbooth]

Although this issue is triaged, the external label relates to the existing tooling such as IDE support. While compilation succeeds, this new syntax trips up Visual Studio, Rider, and even scratch pads such as RoslynPad and LINQPad. This will hinder the development process until this new syntax is accepted.