Removed obsolete-attribute from ConfigureNLog-methods for ILoggingBuilder

[snakefoot]

Reverting #257. Since it will no longer generate double logging after #459

Also fixed ILoggingBuilder.ConfigureNLog()-methods so they can work alone without IHostBuilder.UseNLog().

See also: dotnet/AspNetCore.Docs#14554

[304NotModified]

I'm doubting about this. Afaik it's still bad practice to use both? Nothing goes wrong but it's still obsolete IMO

[snakefoot]

The ILoggerBuilder interface is not obsolete. And you are not required to use IHostBuilder.

[snakefoot]

But it would be nice to have a better fluent-interface-integration with ILoggerBuilder and IHostBuilder to load the NLog-config-file depending on environment (Ex. NLog.Dev.config and NLog.Production.config)

Not everyone setup logging upfront before building the IHostBuilder (Ex want to load environment specific nlog.config). With NetCore3 you will have a lot of confused people that can no longer use ILoggerFactory. Instead a good alternative would be ILoggerBuilder.

[snakefoot]

I believe it should be possible to setup NLog as LoggingProvider directly on LoggerFactory.Create:

var loggerFactory = LoggerFactory.Create(builder =>
{
    builder.ConfigureNLog("NLog.config");
});
ILogger logger = loggerFactory.CreateLogger<Program>();
logger.LogInformation("Example log message");

And Microsoft recommends that logging is setup for IHostBuilder using IHostBuilder.ConfigureLogging:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureLogging(logging =>
        {
            logging.ClearProviders();
            logging.ConfigureNLog("NLog.config");
        })
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
        });

[304NotModified]

Ok merged! thanks!