Fix server rebuilds when adding sub sections especially on Windows

Fix server rebuilds when adding sub sections especially on Windows

This commit also optimizes for the case where change events for both file (e.g. `_index.md`) and the container directory comes in the same event batch.

While testing this on Windows 11 (ARM64), I notice that Windows behaves a little oddly when dumping a folder of files into the content tree; it works (at least after this commit), but it seems like the event batching behaves differently compared to other OSes (even older Win versions).

A related tip would be to try starting the server with polling, to see if that improves the situation, e.g.:

```
hugo server --poll 700ms
```

Fixes #12230