This adds a new expectation test suite which mimics the modular
compilation strategy used by dartdevc; the test code is fully compiled
but the linked dependencies are only compiled as outlines.
Change-Id: I4b8a68087997c025eb39aec414ee1706ddf7f847
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/222762
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>