Mock a MemoryError failure in the failure callback MR test

[bdice]

We could mock a memoryerror failure by having a callback resource that just raises on allocate if we wanted to.

Originally posted by @wence- in https://github.com/rapidsai/rmm/pull/2025#pullrequestreview-3207017187

This is a good idea, and would allow us to work around the issues observed when testing integrated memory systems. With this, we could revert the test skips in #2025.