Support parallel task execution

We use grinder for dartdoc. We have a few lengthy tasks that can be run in parallel. If any of the tasks fail, we want to fail the build.

Is there an easy way to run multiple tasks in parallel? I mean literally in parallel via isolates.

Thanks!

The issue names no files, tests, or entry points. Start by locating Grinder's task execution implementation and existing tests, then determine how isolate-based parallel execution and failure propagation should fit; done means independent tasks run in parallel and any failure fails the build.

Written by the indexing model from the issue text.