Log unhandled exceptions thrown from command actions (#2114)

This PR adds explicit stderr logging for any exception thrown out of an
ImageBuilder command's action handler.

The root cause is that `System.CommandLine`'s default exception handler
silently swallows `OperationCanceledException` (and
`TaskCanceledException`, which derives from it), returning exit code 1
with zero diagnostic output. This makes any failure that surfaces as a
cancellation invisible in pipeline logs (e.g. `HttpClient` timeout). The
`check-base-image-updates` pipeline has been failing this way: after
`READING MANIFEST`, the process exits 1 with no stack trace.

This PR wraps the action body in `Command.TOptions.cs` with a try/catch
that writes the full exception to `Console.Error`.

Upstream issue: dotnet/command-line-api#2808

Author: lbussell

src/ImageBuilder/Commands/Command.TOptions.cs

@@ -4,8 +4,6 @@
 
 using System;
 using System.CommandLine;
-using System.CommandLine.Parsing;
-using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.DotNet.ImageBuilder.Commands
@@ -33,15 +31,29 @@ public Command GetCliCommand()
 
             cmd.SetAction(async (parseResult, cancellationToken) =>
             {
-                options.Bind(parseResult);
+                try
+                {
+                    options.Bind(parseResult);
+
+                    if (!options.NoVersionLogging)
+                    {
+                        LogDockerVersions();
+                    }
 
-                if (!options.NoVersionLogging)
+                    Initialize(options);
+                    await ExecuteAsync();
+                }
+                catch (Exception ex)
                 {
-                    LogDockerVersions();
+                    // System.CommandLine silently swallows OperationCanceledException and TaskCanceledException, so
+                    // log all unhandled exceptions to stderr here and re-throw. This makes sure failures are always
+                    // observable in pipeline logs.
+                    // For more details, see https://github.com/dotnet/command-line-api/issues/2808.
+                    Console.Error.WriteLine($"Unhandled exception in command '{this.GetCommandName()}':");
+                    Console.Error.WriteLine(ex.ToString());
+                    Console.Error.Flush();
+                    throw;
                 }
-
-                Initialize(options);
-                await ExecuteAsync();
             });
 
             return cmd;