Avoid configuring DI for ILogger<T> in tests

[deansheather]

In some test code we are creating a host application builder and instantiating serilog to do app logging.

coder-desktop-windows/App/Services/MutagenController.cs

Lines 160 to 162 in a6f7bb6

	var builder = Host.CreateApplicationBuilder();
	builder.Services.AddSerilog();
	_logger = (ILogger<MutagenController>)builder.Build().Services.GetService(typeof(ILogger<MutagenController>))!;

We should probably just write an implementation for ILogger and ILogger<out T> that log to the test output. It can use serilog under the hood if that makes it easier.

IDK where we'd put it, though. Maybe we should add add a Test.Utils project or something