Remove `computeAt` in unit tests

In the past, we used computeAt as our scheduling primitive. computeAt has been deprecated. However, there are still many unit tests using computeAt. We should replace computeAt in these tests with more modern primitives like TransformPropagator and inlining. A good task that can help gain some understanding of our scheduling primitives can be to pick a test with computeAt and clean up that test.