[infra] Move commands from isolates to gen_tasks.go

This has the side effect of bundling recipes for all tasks,
which will be required anyway to run recipes in the future.

Bug: skia:7050
Change-Id: Ia30a95c750f2a237a8bf60263b2981682673c043
Reviewed-on: https://skia-review.googlesource.com/81300
Commit-Queue: Eric Boren <borenet@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
39 files changed