Simplify HostApplicationLifetime handling in BotApp.cs

Reordered retrieval of HostApplicationLifetime service to occur
after starting hosted services. Removed individual and global
ApplicationStopping event registrations. Called NotifyStarted
on hostApplicationLifetime post hosted services startup. These
changes streamline the startup process and reduce redundant
event handling.

Author: bvdcode

Sources/TelegramBot/BotApp.cs

@@ -118,22 +118,12 @@ public async Task StartAsync(CancellationToken cancellationToken = default)
                 throw ex;
             }
             var hostedServices = _serviceProvider.GetServices<IHostedService>();
-            var hostApplicationLifetime = _serviceProvider.GetRequiredService<HostApplicationLifetime>();
             foreach (var hostedService in hostedServices)
             {
                 await hostedService.StartAsync(mergedToken);
                 _logger.LogInformation("Started '{hostedService}'.", hostedService.GetType().Name);
-                hostApplicationLifetime.ApplicationStopping.Register(() =>
-                {
-                    _logger.LogInformation("Stopping '{hostedService}'...", hostedService.GetType().Name);
-                    hostedService.StopAsync(mergedToken).Wait();
-                });
             }
-            hostApplicationLifetime.ApplicationStopping.Register(() =>
-            {
-                _logger.LogInformation("Application stopping event received.");
-                _cancellationTokenSource.Cancel();
-            });
+            var hostApplicationLifetime = _serviceProvider.GetRequiredService<HostApplicationLifetime>();
             hostApplicationLifetime.NotifyStarted();
         }