Add tests for DI backwards compatibility changes

Some recent changes were made to ensure we maintained backwards compatibility for a targeted set of scenarios using DI. Those changes were made in the `JobHostScopedServiceProviderFactory` type and we need to have a set of tests validating their behavior to ensure it isn't regressed.

Start by locating the JobHostScopedServiceProviderFactory type and reviewing the recent dependency-injection compatibility changes referenced in the issue. Find the host's existing tests for this type or DI behavior, then add coverage for the targeted backwards-compatibility scenarios so the changed behavior is validated and regressions are detected.

Written by the indexing model from the issue text.