generator: use suite criticality from config and parent builder criticality

This allows me to remove the awful hack for making test suites
noncritical. Now we can do that straight in
target_test_requirements.star

BUG=None
TEST=local run, unit tests

Change-Id: I457b890b2257b8ea3a0934de9c34ea12cd45cbb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/go/+/1919465
Reviewed-by: Dhanya Ganesh <dhanyaganesh@chromium.org>
Commit-Queue: Sean Abraham <seanabraham@chromium.org>
Tested-by: Sean Abraham <seanabraham@chromium.org>
1 file changed