[doc] Update dartlang.org links to dart.dev
[doc] Update dartlang.org links to dart.dev

Also update dartbug.com to github issue tracker.

Closes https://github.com/dart-lang/sdk/pull/41370
https://github.com/dart-lang/sdk/pull/41370

GitOrigin-RevId: 806eca0430dc73612b7add9d90aa964ea54e6653
Change-Id: Ibbf490e3ffcf232d3d1d16cf49b753f870d66c80
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/142640
Reviewed-by: Kevin Moore <1d6e7d10d051cf619c5282da3c28fd8d3e0a65a4@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk