[BUG] Leaks and Double Frees in Unit Tests

[revans2]

Describe the bug
I recently ran the unit tests on my desktop and noticed that there were a few leaks and double frees happening.

• One of the leaks appears to be in the RapidsDiskStore and is fixed by Have host spill use the new HostAlloc API #9257
• Another is from GpuColumnarToRowExec, and appears to be that the unit test didn't drain all of the data and because there is no task context the task completion code didn't run to clean it up.
• The final one is a double free that is happening in GpuCoalesceBatchesSuite.scala:751 which is called from line 674 and is a part of test("test entering filtering mode with not enough nulls"). It looks like the test is expecting an exception to be thrown and it is probably a bug in our exception handling that needs to be looked into.