SerilogMessageFormatter CTOR is private, can't be instantiated as the default LogMessageFormatter

[Aaronontheweb]

The formatter will get cached and reused automatically, once per ActorSystem instance, so there's no need for these types of singleton patterns anymore:

Akka.Logger.Serilog/src/Akka.Logger.Serilog/SerilogLogMessageFormatter.cs

Lines 18 to 26 in 0577337

	public static readonly SerilogLogMessageFormatter Instance = new();
	/// <summary>
	/// Initializes a new instance of the <see cref="SerilogLogMessageFormatter"/> class.
	/// </summary>
	private SerilogLogMessageFormatter()
	{
	_templateCache = new MessageTemplateCache(new MessageTemplateParser());
	}

We should delete that optimization and make the default constructor public