Minor tidy up extracted from auto-reconnect change (#9589)
Some minor changes extracted from https://github.com/flutter/devtools/pull/9587, since that review got quite big and I want to simplify it a bit.
- Exclude nested SDK from being analyzed in VS Code
- Fix path in DTD task (it was correct for inside the `packages` folder but was moved to the root without updating)
- Update release notes + template to not say "general updates" in all sections (when only one of them was general)
