In SERVER-41809, we collapsed the unit tests on a per-directory basis in order to improve the build time for the statically linked unit tests, particularly on Windows. However, the collapse was not applied under src/mongo/db/storage, since those tests have specialized setup that renders them incompatible with living together within one binary.

We should investigate how much additional build time savings would result from combining them. If there is real savings, we should undertake the work to make the unit tests compatible with collapse and collapse them.

Doing so would probably also simplify the tests themselves.