Add APIs to support .NET generic host

[smdn]

Description

Add support for building Munin-Node hosted service integrated with the .NET generic host.

This PR adds a new package/assembly/namespace Smdn.Net.MuninNode.Hosting.

In this PR, the following key API will be added:

• AddHostedMuninNodeService(): An extension method to IServiceCollection to register MuninNodeBackgroundService, as described below, which runs Munin-Node as a hosted/background service. The service to be registered is configured using the APIs from Smdn.Net.MuninNode.DependencyInjection. See Add APIs to support dependency injection #17 for detail.
• MuninNodeBackgroundService: The class extends BackgroundService to run Munin-Node as a hosted/background service. It holds a configured and built IMuninNode, and calls IMuninNode.RunAsync to start Munin-Node background tasks.

An example of using the API to be added is as follows:

var builder = Host.CreateApplicationBuilder(args);

builder.Services.AddHostedMuninNodeService(
  options => {
    options.HostName = "munin-node.localhost";
    options.UseAnyAddress(port: 12345);
    options.AllowFrom([IPAddress.Parse("192.168.2.0"), IPAddress.Loopback]);
  },
  nodeBuilder => nodeBuilder
    .AddPlugin(PluginFactory.CreatePlugin(...))
    .AddPlugin(serviceProvider => PluginFactory.CreatePlugin(...))
    .UseSessionCallback((INodeSessionCallback)new(...))
    .UseListenerFactory((IMuninNodeListenerFactory)new(...))
);

Considerations

It is noted that the implementation to be added with this PR is based on ideas proposed in the discussion #11 and PR #12.

This PR is based on #17. It needs to be merged.