Replace code generators with C# 14 extensions

[BeanCheeseBurrito]

The extension code generators should be replaced with the C# 14 extensions feature when it lands. This will get rid of about 400,000 lines of generated code and make the wrapper significantly easier to maintain and contribute to as we will only have to write extension methods once and have it be usable by many types.
https://github.com/dotnet/csharplang/blob/main/proposals/extensions.md

public struct Entity : IEntity { ... }
public struct Component<T> : IEntity { ... }
public struct System<T, ...> : IEntity { ... }
public struct Observer<T, ...> : IEntity { ... }

public static class EntityMethods
{
    // All types that implement the IEntity interface will receive .Get and .Set methods.
    extension<T> (T entity) where T : IEntity
    {
        public ref TComponent Get<TComponent>()
        {
            ...
        }
        
        public ref T Set<TComponent>(TComponent value)
        {
            ...
        }
    }
}

[BeanCheeseBurrito]

Apparently this is already possible with the current C# instance extension syntax. Wasn't aware of this and will begin getting rid of most of the extension source generators.

[BeanCheeseBurrito]

Current extension syntax doesn't work well with methods that have type parameters.

public static class EntityMethods
{
    public static TEntity Add<TEntity, T>(this TEntity self) where TEntity : IEntity
    {
        return self.Add(Type<T>.Id(self.World));
    }
}

// Both type parameters must be passed.
Entity e = world.Entity();
e.Add<Position>(); // Invalid
e.Add<Entity, Position>(); // Valid

Will have to wait until the new extensions feature in .NET 10.