Add nightly CI jobs that build in debug mode

As a user of CCCL, I want to be able to compile my code using CCCL in debug mode and for it to compile and run correctly.

CCCL does not test debug builds today, therefore we have no guarantee that they work.

We should add jobs to our CI to verify that debug builds work as expected.

It's likely these jobs will be very expensive, so they should initially just be nightly jobs.