[ VM / DartDev ] Re-enable DartDev
[ VM / DartDev ] Re-enable DartDev

This reverts commit a71449925a43177e2a8f3442c71f1f4780e506a2.

Reason for revert: 2.8 has been branched.

Original change's description:
> [ VM / DartDev ] Disable DartDev for the 2.8 release
> 
> Change-Id: I0b2d588599bee57b546c304b61c3edf1bc92f64c
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/141020
> Reviewed-by: Jaime Wren <cd1ab83d11dd618c6b8cd01592020d0bd5183fdc@google.com>
> Commit-Queue: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@google.com>

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I1593bece22a096956588196bf9a50d2ace4ad580
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/142400
Reviewed-by: Jaime Wren <cd1ab83d11dd618c6b8cd01592020d0bd5183fdc@google.com>
Commit-Queue: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@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