Add test coverage for migrations looking at the code generated in Up and Down methods

Most of the migration tests we have look at the migration SQL and the model that is produced as a result. However we could also use some (end-to-end) test of the migrations code. From what I saw we only have one smoke test, making sure the code compiles.

Example of what the test could help with is in temporal tables - we add a lot of annotations to temporal migration operations, some of those annotations may not be necessary or cause the migration code to be "ugly".