Determine pattern of tooling go links and create important ones

[parlough]

If you have destinations you currently (or would like to) link to from tooling, please comment here with the destination/topic/reason or similar. Thanks!

[DanTup]

These are the URLs I found in the Dart-Code currently (some are Dart, but since I had them I thought I'd post them for completeness):

• https://dart.dev/get-dart
• https://dart.dev/tools/dart-devtools
• https://dart.dev/tools/pub/glossary#system-cache
• https://docs.flutter.dev/f/flutter-survey-metadata.json
• https://docs.flutter.dev/get-started/install/linux#update-your-path
• https://docs.flutter.dev/get-started/install/macos#update-your-path
• https://docs.flutter.dev/get-started/install/windows#update-your-path
• https://flutter.dev/docs/development/tools/web-renderers
• https://flutter.dev/setup/
• https://api.flutter.dev/flutter/${sample.libraryName}/${sample.className}-${suffix}.html${fragment}

The last one is used to power the "Open interactive sample" CodeLens feature. We get the library/classname from the analyzers Outline data (and use class, mixin or extension-type as a suffix based on the element kind, and build a matching fragment like "widgets.RestorationMixin.1" to scroll down to the embedded sample.

[parlough]

In the various linked PRs, I've added tooling /to/ links for links already used in the tool and framework, and with flutter/flutter@b6cd31e, https://github.com/flutter/flutter/blob/main/docs/contributing/use-reliable-links.md now has guidelines on adding and using them.