Support Auto Debug Mode

This is the current code:
https://github.com/getsentry/sentry-dotnet/blob/6274944d00826b0442d038f675f4f46ac0fec182/src/Sentry/SentryOptions.cs#L620-L668

What this effectively does, AFAICT, is that we don't print any warnings when `Debug` is not set. That is pretty unexpected behavior, at least to me, especially considering what the docs say when you're setting up sentry:

```
// When debug is enabled, the Sentry client will emit detailed debugging information to the console.
// This might be helpful, or might interfere with the normal operation of your application.
// We enable it here for demonstration purposes when first trying Sentry.
// You shouldn't do this in your applications unless you're troubleshooting issues with Sentry.
options.Debug = true;
```

Instead, I'd expect the DiagnosticLogger property to always be reachable. It already has a check which log levels should be printed.