`UseExceptionHandler` exit code is not honored when a custom delegate is provided

When both a custom `errorExitCode` value **_and_** a custom handler delegate are passed to `UseExceptionHandler`, and an exception is thrown by the handler, then the custom exit code is not honored.

```csharp
var rootCmd = new RootCommand();
rootCmd.SetHandler(_ => throw new Exception());

var parser = new CommandLineBuilder(rootCmd)
.UseExceptionHandler(
(_, _) => { },
errorExitCode: 42)
.Build();

var exitCode = parser.Invoke("");

exitCode.Should().Be(42);
// ACTUAL: 0
```

See: https://github.com/dotnet/command-line-api/issues/796#issuecomment-1273848670